Whereas Nixon focuses on to justify a new therapeutic agent on its cost effectiveness buy 250mg chloramphenicol mastercard, 1188 Neuropsychopharmacology: The Fifth Generation of Progress this kind of discussion is increasingly becoming a part of ter by Small chloramphenicol 500 mg without a prescription, Morley discount chloramphenicol 250mg amex, and Buchan points out, have not been drug development. Nevertheless, as this chapter details, Since the publication of the Fourth Generation of Progress, this is a particularly rich area of experimental therapeutics the recognition of Lewy body dementia has increased sub- and one of the best examples of the ways in which funda- stantially. To many clinicians, this is a diagnostic entity that mental advances in neuroscience can drive rational drug was previously incorrectly diagnosed as either Alzheimer dis- development. This theme is made all the more apparent ease with some parkinsonian features or Parkinson disease when Chapter 92, by Graham and Hickey, is read alongside with dementia. In a wonderfully lucid chapter (Chapter 91), Chapter 93, because the former so elegantly summarizes the McKeith et al. Alzheimer disease and provide a detailed account of the Highly active antiretroviral therapy (HAART) has revo- clinical features discovered in the 1990s. Evans and Mason address both the neurocognitive responsible for characterizing the molecular and cellular pa- functioning and the psychiatric manifestations of HIV-1 thology of these conditions has contributed a key chapter infection, as well as its treatment in the HAART era. In Chapter 94, Higuchi, Trojanowski, and Taken together, the chapters in this section are an im- Lee address tau-positive filamentous lesions in neurodegen- pressive compendium of advances in understanding and erative disease. That One of the most active areas of central nervous system so much has been learned in so short a time is truly remark- therapeutics has been in developing drugs to decrease the able, but even more remarkable is the advances that will cellular disease that follows stroke. Many drugs have shown undoubtedly occur in the future, advances whose founda- promise in what seem valid animal models, but, as the chap- tions are eloquently elaborated in the following pages. MOHS VAHRAM HAROUTUNIAN INTRODUCTION TO THE NATURAL HISTORY AD patients, and behavioral problems have been linked to an increased need for health services including nursing Alzheimer disease (AD) is a progressive, degenerative brain home care. Clinically, patients with AD have impairments in and are difficult to differentiate from the mild memory loss memory, language, praxis, and other cognitive functions that is a frequent consequence of normal or usual aging. Longi- Inevitably, however, the degenerative changes of AD be- tudinal studies leading to autopsy have shown that the most come sufficiently severe so the patient has difficulty with common neuropathologic findings in elderly patients with daily functioning. The functional change can be observed these symptoms are neuritic plaques (NPs) and neurofibril- first in the performance of cognitively demanding tasks such lary tangles (NFTs). Modern diagnostic criteria for AD rec- as handling money, remembering appointments, following ognize that AD is both a clinical and pathologic entity. To differentiate AD from other acquired neu- patients are often unable to remember even very simple ropsychiatric conditions associated with cognitive impair- things, have great difficulty talking and understanding lan- ment, the clinical diagnosis of AD is only made when no guage, and may be confined to bed or to a chair. Patients who meet the clinical criteria sis is approximately 10 years, but with a great deal of vari- for AD are very likely to have the characteristic neuropathol- ability around that mean. Sometimes, however, the clinical diag- In the sections that follow, we review studies of the devel- nosis is not confirmed at autopsy, and hence the most widely opment of the neurobiological changes responsible for AD. In each section, we emphasize the need to understand AD Although progressive cognitive impairment is the core from a longitudinal perspective because both the underlying or defining characteristic of AD clinically, patients with this neurobiology and clinical presentation of the illness vary disease have other symptoms as well. Many patients also substantially across the course of illness. Because of intense have other neuropsychiatric symptoms including agitation, recent interest in understanding the very early development psychosis, depressed mood, and personality change. These of AD to develop preventive therapies, our presentation em- other symptoms are not necessary for a diagnosis of AD phasizes recent findings on the earliest manifestations of and tend to be quite variable both within a given patient disease. When they are present, these symptoms can be a major problem for caregivers of NEUROBIOLOGICAL STUDIES ACROSS THE SEVERITY SPECTRUM Richard C. Mohs and Vahram Haroutunian: Research Service, Mount It has already been noted that the definitive diagnosis of Sinai School of Medicine, Veterans Affairs Medical Center, Bronx, New York. AD depends on neuropathologic changes that characterize 1190 Neuropsychopharmacology: The Fifth Generation of Progress the disease. No single neuropathologic lesion is in itself ade- with AD. How- quate for the diagnosis of AD; rather, the neuropathologic ever, these lesions are not exclusively associated with AD. The absolute weight of mented elderly persons and in association with non–AD- the brain is decreased relative to normal controls, but this like neurodegenerative diseases (17). Although NP and decrease is generally less than 10% relative to age-matched NFT lesions can be present in diseases other than AD, other controls, and it is neither diagnostic of nor specific to AD markers and clinical phenotypes can be used to distinguish (1). Gross examination of the brain in AD also reveals signif- among them, and the presence of NPs and NFTs in the icant apparent atrophy, widening of the sulci, and erosion absence of other confounding neuropathologic lesions pro- of the gyri, but these changes also reflect advanced age with vides the basis for the diagnosis of AD. NPs are extracellular deposits of varying sizes with an However, the atrophy of the cortex is associated with signifi- amyloid -peptide core (A ) and neuritic inclusions. A is cant reductions in the numbers of neurons (2,3). For exam- a 40 to 43 amino acid long peptide that is generated from ple, Terry et al. Similarly, Gomez-Isla and col- that lead to the production of A from APP are under leagues (5,6), using unbiased stereologic sampling tech- intense investigation. Cleavage at the C- losses in specific cortical laminae. These neuronal losses were terminus is attributed to an as yet unidentified enzyme observed not only in brain specimens from patients with termed -secretase. Some evidence suggests that presenilin severe dementia, but also in specimens derived from patients 1 may be the -secretase (22), but this hypothesis is still with relatively mild or questionable dementia. That A deposition plays a critical role tude of neuronal loss increases systematically with increasing in the pathogenesis of AD was recognized with the accumu- dementia severity and increasing disease duration. Neuronal lation of evidence showing that mutations in the APP gene, degeneration is not restricted to the cortex, but it is also as well as mutations in the gene encoding for presenilin 1 reflected in neuronal losses in subcortical nuclei such as the and 2, were invariably associated with AD (23,24). Studies nucleus basalis of Meynert (7) (the cells of origin of the in transgenic mice demonstrated that the introduction of cholinergic input to the cerebral cortex), the locus ceruleus, these mutations leads to the development deposition of A and raphe aminergic nuclei (8,9). Neuronal loss in these plaques and learning and memory deficits in some mutants subcortical structures, especially in the nucleus basalis of (25–27). Meynert (10), has also been found to correlate significantly Despite the clear evidence implicating NP deposition with dementia severity and cognitive deficits. Although (dementia) during the early phases of the disease. Ascertain- synaptic markers such as synaptophysin are reduced signifi- ment of the relationship between specific pathologic lesions cantly in the cerebral cortex, especially the frontal and pari- and symptoms of AD has been difficult, because most stud- etal cortices and in the hippocampus, with increasing age ies have focused on the neuropathology of AD at the termi- (11), further losses are encountered in AD, whether assessed nal stages of the disease, when dementia has been fully devel- by immunohistochemical techniques or by direct assessment oped and neuropathologic lesions have been profuse. The loss Studies have suggested that increases in the densities of neo- of synaptophysin immunoreactivity in the frontal and pari- cortical NPs occur very early during the course of cognitive etal cortices, and in the hippocampus, is among the strong- deterioration (6,10,28–32), and they may be among the est correlates of dementia severity (10,15,16). These losses initial pathologic events in the development of AD (31). This loss of synaptic markers of NPs and A immunoreactivity were then quantified in is not merely a reflection of the degeneration of the cortical different brain regions. These studies showed that increases neurons noted earlier, but it also reflects the loss of presy- in NP density and quantitatively measured A immuno- naptic terminals and neuropeptide-and neurotransmitter- reactivity are evident even in those patients who die at the containing vesicles. The density of NPs and A Chapter 82: Alzheimer Disease: From Earliest Symptoms to End Stage 1191 immunoreactivity then increase systematically as a function and indices have been observed (41). In one study (29), elevated neurochemical deficits are deficits in neocortical indices of levels of A -42 were detected in multiple neocortical re- cholinergic function and decreases in the concentrations of gions before NFTs and significant immunoreactivity to ab- several neuropeptides such as somatostatin and corticotro- normal tau (see later) could be demonstrated in the same pin-releasing hormone (42). Increases in NP density and A immuno- chemicals and neurotransmitters such as norepinephrine reactivity were observed in cases of mild dementia before and serotonin have also been reported, but their alterations the density of neuropathologic lesions was high enough for are not as profound and do not appear to be as consistently the patients to meet the threshold criteria for the definitive observed (41,43,44). Deficits in the activity of cholinergic diagnosis of AD. Immunohistochemical and biochemical studies have 46). Deficits in cortical cholinergic marker enzymes have shown that NFTs consist of paired helical filaments that been among the most consistently replicated neurochemical are abnormal aggregates of abnormally folded (33,34) or findings in AD. Some studies have reported that compensa- phosphorylated (35,36) forms of the microtubule-associated tory mechanisms interact with cholinergic enzyme deficits protein tau. The progressive involvement and distribution and lead to an up-regulation of high-affinity choline trans- of NFTs to different brain regions have been used to stage port (47). Irrespective of compensatory mechanisms that the neuropathologic severity of AD (37,38). These studies may be engaged, the loss of cortical cholinergic enzyme have suggested that the first signs of NFT are found within activity is associated with severe degeneration of cholinergic the entorhinal cortex, followed by the hippocampus, and the neurons in the basal forebrain including the neocortically eventual involvement of virtually all regions of the isocortex. There is also clear evidence that the density and severity of The discovery of these profound forebrain cholinergic sys- NFTs increase as a function of increasing disease duration tem deficits and the growing understanding of the role of (5,6).
Neuroendocrine mechanisms were im- to clomipramine or SSRIs and approximately 40% of them plicated in the pathogenesis of obsessions and compulsions 500mg chloramphenicol with mastercard, have no clinical improvement (55 safe chloramphenicol 250mg,56) may reflect the bio- based on studies employing oxytocin buy 250 mg chloramphenicol with visa, vasopressin, and so- logical heterogeneity of the OCD phenotype already sug- matostatin (64,80–82). These studies also need further rep- gested by the variability of the response to acute 5-HT chal- lication. Thus, consideration of more homogeneous subgroups of OCD patients defined by response to biologi- The Autoimmune Hypothesis cal challenges or different symptom subtypes could lead to clarification of the pathogenesis of the disease and the role Allen, Leonard, and Swedo first proposed the intriguing of alternative hypotheses to the serotonergic one. An association was drawn between infection with group A -hemolytic Streptococcus (as well The Dopamine Hypothesis as other agents, including viruses), and the onset or the There is now considerable evidence that some forms of exacerbation of OCD in some children. The observation of OCD are etiologic related to GTS (57). When a diagnosis of obsessive coccus-induced autoantibodies reacting with the basal gan- symptoms was used, these investigators found that 87% of glia) and OCD led to the characterization of the 'pediatric the MZ twins were pair wise concordant compared to 47% autoimmune neuropsychiatric disorders associated with of DZ twins, yielding a heritability estimate of approxi- streptococcal infections' (PANDAS) by Swedo and col- mately 80%. Similar links between In a more recent study, Torgersen (94) investigated the group A -hemolytic Streptococcus and GTS have been concordance of anxiety disorders (including obsessive-com- observed (86,87). A monoclonal antibody that identifies B- pulsive disorder) in the co-twins of 32 MZ and 53 DZ same- lymphocyte antigen (D8/17) has been shown to be a marker sex Norwegian twins. The sample consisted of all twins born for susceptibility to rheumatic fever, PANDAS, and early- between 1910 and 1955 who were admitted for treatment onset OCD in general (88,89). Moreover, D8/17 levels have of neurotic or borderline psychotic disorders at any time been found to follow a segregation pattern most consistent before 1977. After ascertainment each twin was interviewed with autosomal recessive inheritance in rheumatic fever using a structured psychiatric interview that recorded life- families (89,90). There is evidence that PANDAS is familial, time occurrence of psychiatric symptoms; this information with dramatically increased rates of clinical and subclinical was then combined with the hospital records to make DSM- OCD observed in parents of children with PANDAS (91). A group of six DSM-III anxiety disor- The importance of this hypothesis cannot yet be deter- ders was examined: panic disorder, agoraphobia with and mined, however, because it is not known how many child- without panic, social phobia, OCD, and generalized anxiety hood-onset cases of OCD are associated with this autoim- disorder (GAD). It is possible that inherited genetic factors for the same anxiety disorder. Thus, the author examined interact with the autoimmune mechanisms, making a sub- concordances in the larger context of an 'anxiety spectrum. Genetic variants in the human leukocyte phobia, social phobia, and OCD was, a statistically signifi- antigen (HLA) system may be interesting candidates to ex- cant difference in concordance rates was seen: 45% in MZ amine in this group of OCD subjects. This differ- ence was not seen when considering GAD alone, nor when a combined proband diagnostic category including GAD THE GENETICS OF OCD was used. Two important aspects of these studies critically limit There has been considerable controversy regarding the in- their usefulness. The first limitation is the lack of standard- heritance of OCD. This is surprising since the familial na- ized diagnostic criteria across studies. It is difficult to inter- ture of OCD has been documented since the 1930s and pret results when different diagnostic criteria are used in twin studies have provided evidence for the importance of the different studies being compared. The second limitation genetic factors in the manifestation of OCD. The investi- gators doing the evaluations of the co-twin, knew the diag- nosis of the index case. The lack of any procedural blind for Twin Studies obtaining diagnostic information or for making the actual In 1986, Rasmussen and Tsuang (92) reviewed the literature diagnoses of a co-twin is a serious source of bias that could on OCD twins and found 32 of 51 (63%) MZ twins were lead to spurious results. Furthermore, when those twins Two studies were completed that used twins ascertained where zygosity was in doubt were eliminated from the sam- through twin registries. Furthermore, the evaluations of the ple, 13 of 20 (65%) were concordant for OCD. Clifford (95) and Clifford and concordance rates are similar to those reported for affective associates (96) analyzed data collected from 419 pairs of and anxiety disorders. However, the results need to be inter- unselected twins who had been given the Eysenck Personal- preted with caution because no data from DZ twins were ity Questionnaire (EPQ) and the 42-item version of the available for comparisons. Multivariate analyses This shortcoming was addressed by Carey and Gottes- provided separate heritability estimates of 44% for obses- man (93) who studied a consecutive series of 15 MZ and sional traits (as defined by the 10-item 'Trait Scale' of the 15 DZ twins ascertained from the Maudsley Twin Register. LOI) and 47% for obsessional symptoms necessary for a The index twin in each pair had received a psychiatric diag- diagnosis of OCD (as defined by the 32-item 'Symptom nosis of obsessional neurosis, obsessional personality, or Scale' of the LOI). In a separate study using twins from phobic neurosis at local hospitals during a 32-year interval the Australian Twin Registry, Andrews and associates (97) (1948 to 1979). Each twin pair was followed-up by personal administered structured psychiatric interviews to 186 MZ interview and assessment of psychiatric status. Lifetime data for OCD, GAD, panic 1612 Neuropsychopharmacology: The Fifth Generation of Progress disorder, social phobia, and major depressive disorder were adult OCD probands. The findings were similar to those of Torgersen in of 18 of 32 probands with OCD and 33 controls were that, no differences in MZ/DZ concordances were observed systematically interviewed using the Diagnostic Interview when individual disorders were examined. Altogether, 249 relatives (nearly 60%) were the diagnoses were combined into a single category of 'neu- directly interviewed. Although the prevalence of OCD was roticism,' the MZ correlations were significantly higher not significantly increased among relatives of OCD pro- than for the DZ twins; (0. In particular, there was an increase in the rate of 'subclini- In summary, all twin studies to date are consistent with cal' OCD among parents of OCD probands when com- the hypothesis that genetic factors are important for the pared to parents of controls. The following caveat should expression of OCD and the specific symptoms necessary be noted when interpreting these findings. Furthermore, the two most recent of psychiatric disorders, direct interviews, family history studies (94,97) suggest that some of the same genetic factors data, and medical record data are used to make 'best esti- may be important for the manifestation of some other anxi- mate' diagnoses (104). Given the secrecy of many OCD patients and their tendency to hide their Family Studies illness, it is possible that some family members denied symp- Data from the majority of family studies completed over tomatology on direct interview. As noted in the report, fam- the past 60 years suggest that OCD is familial (7); however, ily history data were collected by Black and colleagues but rates of illness among relatives vary from study to study. When Many of the studies completed prior to 1990 are difficult those family history data are included, the recurrence risk to interpret because of differences in diagnostic criteria and among first-degree relatives is 9. Some of the Using this estimate for the risk to relatives, the ranges shortcomings of this early research were addressed in six between 1. All of these studies demonstrate In 1995, Pauls and colleagues (57) reported the results that OCD and related conditions are familial. The age corrected rate of dren and adolescents and found that 17% of the parents OCD (10. In a second OCD probands when compared to controls (1. A fa- study of the families of children and adolescents, Leonard milial relationship has been reported between OCD and and co-workers (99) found that 13% of first-degree first- GTS and chronic tics (CT) (105) and it has been speculated degree relatives of OCD probands met DSM criteria for that familial OCD is that type that is related to GTS. Although this rate is cantly higher among relatives of OCD probands than somewhat lower than other studies, it nevertheless repre- among controls in this study, the patterns within the fami- sents a twofold increase over available population prevalence lies suggested that much of OCD is not related to GTS; estimates. Of note is that when probands were separated the majority of OCD individuals did not have a personal on the basis of age at onset, the morbid risk for OCD among or family history of GTS or tics; however, many did have relatives of early onset (before age 14) probands was 8. A shortcoming of these three studies is that none Finally, in the most recent and methodologically sound included a control sample. However, assessments in all of family study of OCD, Nestadt and colleagues (102) re- them were done using structured interviews that were used ported that 11. The best estimate of the popula- probands met DSM-III-R criteria for OCD compared to tion prevalence for OCD from the most recent epidemio- only 2. The methods used in this study were logic study (103) is 2. That is, the investigators directly interviewed all ington, DC). Using this estimate of prevalence, the relative available first-degree relatives and obtained family history risk ( ) (the ratio of illness among relatives to the population data for all first-degree relatives. Best estimate procedures prevalence) (103) for these two studies ranged between 4. Black and colleagues (101) studied families of 32 Nevertheless, it is remarkable that the estimates of recur- Chapter 112: The Pathophysiology and Genetics of OCD 1613 rence risk obtained in the two studies were not significantly ual, religious and somatic obsessions and related checking different. Using available population prevalence estimates behavior was 23. There was no relationship between reliable and valid, it has also become clear over the last risk to relatives and proband factor scores for the other fac- decade that there is considerable variability of symptomatol- tors. As discussed, results of complex segregation analyses ogy across individuals who have a diagnosis of OCD. Given that incorporated these factors scores suggested that there this variability, a number of investigators have begun re- were different patterns of transmission within families that search to explore the possibility that subtypes/components were related to the factor scores of the probands. Unfortu- of OCD might be distinguished on the basis of some fea- nately, the number of affected relatives for whom it was tures of the disorder.
For more this property in UPD have focused research on long-term than 50 years discount chloramphenicol 500 mg online, lithium cheap chloramphenicol 250mg without a prescription, the prototypal mood stabilizer order chloramphenicol 250mg, has events, such as alterations in gene expression and neuroplas- been known to be effective not only in acute mania but ticity, that may play a significant role in stabilizing the clini- also in the prophylaxis of recurrent episodes of mania and cal course of an illness. By contrast, the preponderance of past research and stabilization stem from the acute pharmacologic effects in depression has focused on the major depressive episode of antidepressants and mood stabilizers; thus, both the acute and its acute treatment. It is only relatively recently that and longer-term pharmacologic effects of both classes of investigators have begun to address the recurrent nature of drugs are emphasized in this chapter. Thus, it is timely that we address in a single chapter the most promising research rele- vant to the pharmacodynamics of both mood stabilizers and MOOD STABILIZERS antidepressants. Effective treatments exist for However, for the purpose of our discussion, it is important the acute phases of both disorders; maintaining both types to differentiate the three clinical phases of BPD—acute of patients on such drugs on a long-term basis decreases the mania, acute depression, and long-term prophylactic treat- likelihood and intensity of recurrences. Further, because the ment for recurrent affective episodes. Although a variety of drugs are given long-term, they produce a cascade of phar- drugs are used to treat BPD (i. Both classes of psychotropic drugs incur a lag that only a drug with properties of prophylaxis should be period for therapeutic onset of action, even in the acute referred to as a mood stabilizer and included in this chapter. Consequently, it is widely subset of patients with BPD 1. However, the data for long- thought that the delayed pharmacologic effects of these term prophylaxis with anticonvulsants (i. The early realiza- In the absence of a suitable animal model, an experimental tion that lithium is effective prophylactically in BPD and approach, used to ascribe therapeutic relevance to any ob- served biochemical finding, is the identification of shared biochemical targets that are modified by drugs belonging to the same therapeutic class (e. Lenox: HeadCNSGroup, AventisPharmaceuticals,Bridgewa- possessing distinct chemical structures (e. Alan Frazer: Department of Pharmacology, University of Texas Health valproate). Although unlikely to act via identical mecha- Science Center, San Antonio, Texas. Mood stabilizers and antidepressant actions: short-term and long-term events. Lithium and antidepressants have acute effects on synaptic signaling that serve to trigger progres- sively longer-term events in signal transduction; these in turn lead to changes in gene expression and plastic changes in brain. The acute affects in critical regions of the brain result in changes in certainbehavioralandphysiologicsymptomatology(e. Subchronic effects lead to amelioration of symptoms related directly to mood, whereas it is thought that the longer-term (chronic)effects underlie the prophylactic properties of these drugs to prevent recurrent affective episodes in both unipolar and bipolar disorders. Thus, in our discussion, we use studies of neurotransmitter to the ability of the monovalent cation to lithium as a prototypal mood stabilizer and cross-reference alter the pattern of signaling in critical regions of the brain evidence for the anticonvulsants when the data are available. It is in this context that we highlight Furthermore, it is important to note that drugs that are the most current thinking regarding putative sites for the useful in the treatment of acute mania or depression may therapeutic action of lithium in the brain, which is heuristic not necessarily have prophylactic properties (1) and, as in and sets the stage for future research directions. Although it is Ion Transport likely that the targets for lithium action early in treatment trigger its long-term properties of mood stabilization, to Ion-gated channels, which are driven by either adenosine what extent the biological mechanisms underlying long- triphosphate (ATP) or the net free energy of transmembrane term lithium prophylaxis contribute to the efficacy of lith- concentration gradients, regulate the distribution of lithium ium in acute mania remain to be demonstrated. These transport systems are criti- Studies through the years have proposed multiple sites cal for the regulation of resting lithium in the bulkcyto- for the action of lithium in the brain, and such research plasm in that they regulate steady-state intracellular ion con- has paralleled advances in the field of neuroscience and the centrations that set the threshold for depolarization in experimental strategies developed during the past half-cen- excitable cells. For the most part, proper interpretation of these data however, by virtue of its high energy of hydration, it can also has at times been limited by experimental design, which has substitute for the divalent cations calcium and magnesium, often ignored not only the clinically relevant therapeutic which may account for some of its major biochemical sites range of concentrations and onset of action of lithium, but of action. Much of the anticonvulsant properties of val- also critical control studies defining its specificity of action proate, carbamazepine, and lamotrigine have been attrib- in comparison with other monovalent cations and classes uted to their ability to inhibit sustained repetitive firing by of psychopharmacologic agents. While the targets for the prolonging the recovery of voltage-gated sodium channels action of lithium have shifted from ion transport and pre- from inactivation (2). However, it is important to note that synaptic neurotransmitter-regulated release to postsynaptic anticonvulsant activity appears to be neither necessary nor receptor regulation, to signal transduction cascades, to gene sufficient for mood stabilization because lithium has pro- expression and neuroplastic changes in the neuropil, the convulsant properties outside its narrow therapeutic range. Chapter 79: Mechanism of Action of Antidepressants and Mood Stabilizers 1141 Although some membrane transport systems specifically Neurotransmitter Signaling/Circadian recognize lithium and regulate its transmembrane concen- Rhythm tration (e. Earlier studies focused on the modulation of pre- ATPase pump has been extensively studied in relation to the synaptic components, including the synthesis, release, turn- membrane transport of lithium and the therapeutic effect of over, and reuptake of neurotransmitters. Based on measure- the focus has shifted to postsynaptic events, such as the ments of lithium in peripheral neurons and synaptosomal regulation of signal transduction mechanisms (see refs. Despite the fact that some of the results ment was found to decrease Na, K-ATPase activity, particu- of the presynaptic and postsynaptic investigations are not in larly in hippocampus (7). Various groups have studied Na, full agreement, at present the evidence supports the action of K-ATPase activity in patients with mood disorders and have lithium at multiple sites that modulate neurotransmission. Despite the fact that clinical studies receptor up-regulation and supersensitivity. In the choliner- through the years have been constrained by relatively small gic system, lithium enhances receptor-mediated responses and often variable findings, evidence has been found that at neurochemical, electrophysiologic, and behavioral levels. Na, K-ATPase activity may be reduced, especially in the Long-term lithium treatment increases GABAergic inhibi- depressed phase of both UPD and BPD, and is associated tion and has been shown to reduce excitatory glutamatergic with an increase in sodium retention (see refs. Furthermore, long-term lithium treatment has been shown to enhance -aminobutyric acid (GABA) signaling, observed to result in an increased accumulation of lithium and the anticonvulsant lamotrigine has been shown to re- and activity of Na, K-ATPase in erythrocyte membranes, duce glutamatergic neurotransmission. It is currently with concomitant reduction of sodium and calcium within thought that the effect of lithium on the spectrum of neuro- erythrocytes in patients with BPD. Because the concentra- transmitter systems may be mediated through its action at tion of free calcium ion tends to parallel the concentration intracellular sites, with the net effect of long-term lithium of free sodium ion, this finding may account for observa- attributed to its ability to alter the balance among neuro- tions that intracellular calcium is increased in patients with transmitter/neuropeptide signaling pathways. Interestingly, when patients with BPD were One of the unique and most robust properties of lithium treated with lithium, Na, K-ATPase activity was found to is its ability to lengthen the circadian period across spe- be increased, consistent with observations of reduced Ca2 cies—unicellular organisms, plants, invertebrates, and ver- after treatment. However, such evidence from blood cells tebrates (including primates)—so that a phase delay in the must be interpreted with caution; more recent data support circadian cycle often results (see refs. It has long been Although a balance of resting lithium conductance and recognized that a dysregulation of circadian rhythms is asso- net transport/efflux mechanisms regulates lithium homeo- ciated with the clinical manifestation of recurrent mood stasis, the ligand gating of ion channels on the time scale disorders in patient populations (see refs. In the tions in sleepiness, alertness, cognitive performance, and local environment of a dendritic spine, the surface area-to- mood (19–22). The early morning awakening, shortened volume ratio becomes relatively large, such that the lithium latency in rapid-eye-movement (REM) sleep, and advances component of a synaptic current may result in significant in hormonal and temperature regulation of many depressed (as much as fivefold to 10-fold) increases in intracellular patients, including those with BPD, are thought by some lithium concentration following a train of synaptic stimuli investigators to indicate a phase advance of the central pace- (11). Such an activity-dependent mechanism for creating maker within the suprachiasmatic nucleus of the hypothala- focal, albeit transient, increases of intracellular lithium at mus relative to other internal oscillators or external zeitgeb- sites of high synaptic activity may play a role in the therapeu- ers (23–27). Lithium may achieve its therapeutic and tic specificity of lithium and its ability to regulate synaptic prophylactic effects by altering the balance of neurotrans- function in the brain. Fur- thermore, because the mode of enzyme inhibition of IMPase Signal Transduction is uncompetitive, likely through interaction with Mg2 binding sites (34), the preferential site of action for lithium Phosphoinositide Cycle was proposed to be on the most overactive receptor-me- Since it was discovered that lithium is a potent inhibitor diated neuronal pathways undergoing the highest rate of of the intracellular enzyme inositol monophosphatase phosphatidylinositol 4,5 bisphosphate (PIP2) hydrolysis (IMPase) (Ki 0. It is also of interest that a number of structurally phosphate to inositol (31,32), receptor G protein-coupled similar phosphomonoesterases that require magnesium have phosphoinositide (PI) hydrolysis has been extensively inves- also been found to be inhibited by lithium at Ki values below tigated as a site for the action of lithium as a mood stabilizer 1mM (37,38). The 'inositol-depletion In cell systems and in cerebral cortical slices of chronically FIGURE 79. Molecular targets for lithium in phosphoinositide (PI)signaling. Pathways depicted within the figure are three major sites for an inhibitory action of lithium: inositol 1-monophospha- tase (IMPase); inositol polyphosphate 1-phosphatase (IPPase); and glycogen synthase kinase 3 (GSK-3 ). Inhibition of IMPase and IPPase can result in a reduction of myo-inositol (myo-Ins)and subsequent changes in the kinetics of receptor-activated phospholipase C (PLC)breakdown of phosphoinositide-4,5-bisphosphatetodiacylglycerol(DAG)andinositol-1,4,5-trisphosphate. Alter- ation in the distribution of inositol phosphates can affect mechanisms mediating presynaptic release. DAG directly activates protein kinase C (PKC), and this activation results in downstream post-translational changes in proteins that affect receptor complexes and ion channel activity and in transcription factors that alter gene expression of proteins such as MARCKS (myristoylated alanine-rich C-kinase substrate), which are integral to long-term neuroplastic changes in cell func- tion. Inhibition of GSK-3 within the wnt-receptor (wnt-R)pathway alters gene transcription and neuroplastic events through an increased expression of downstream proteins such as -catenin. In addition, this inhibition can indirectly affectphosphoinositide 3 kinase pathways and intermediate factors (e. Chapter 79: Mechanism of Action of Antidepressants and Mood Stabilizers 1143 treated rats, the effects of lithium on receptor-coupled PI hibits 50% (IC50) values ranging from 1 to 5mM (see ref. Lithium in vitro inhibits adenylyl cyclase activ- alanine-rich C-kinase substrate (MARCKS) protein ity stimulated by guanosine triphosphate (GTP) or calcium/ (discussed below) can be prevented or reversed by a high calmodulin, both of which interact directly with adenylyl concentration of myo-inositol. These inhibitory effects of lithium are an- Drosophila indicate a role for the upstream inositol polyp- tagonized by Mg2, which suggest that the action of lith- hosphatase (IPPase) as an additional target for lithium (43) ium on the adenylyl cyclase system is mediated by direct (Fig. Drosophila harboring a null mutation for the competition with Mg2(55). However, attenuation of ade- IPPase gene demonstrate aberrant firing of the neuromuscu- nylyl cyclase activity following long-term lithium treatment lar junction, an effect that is mimicked by the treatment of in rat cortical membranes was not antagonized by Mg2 wild-type flies with lithium. Although studies during the alone but was reversed by increasing concentrations of GTP, past several years have provided evidence that myo-inositol which implies that the effect of long-term lithium treatment clearly plays a role in the action of lithium, it is evident may be mediated at the level of G proteins (54,56). In studies examining the in vivo physio- clinically relevant concentration has been shown to produce logic effects of lithium, such as polyuria or enhancement a significant alteration of the AR-coupled cAMP generat- of cholinergically induced seizures, the addition of myo-ino- ing system in cultured cells in vitro. In contrast to long-term sitol reduced but did not fully reverse the lithium-induced lithium (discussed above), long-term valproate was found to effects (44,45).
Journal of Child Psychology and Psychiatry 2003; 44:945-960 discount chloramphenicol 500 mg fast delivery. Meta-analysis of the association between the 7-repeat allele of the dopamine D4 receptor gene and attention deficit hyperactivity disorder order chloramphenicol 500mg amex. Biological Psychiatry 2009; Apr 30 [Epub ahead of print] Froehlich W purchase chloramphenicol 250 mg, Cleveland S, Torres A, et al. Head circumferences in twins with and without autism spectrum disorders. Pharmacologic intervention for attention-deficit hyperactivity disorder in preschoolers: is it justified? A retrospective foetal ultrasound study of brain size in autism. Decreased functional brain connectivity in adolescents with internet addiction. Pediatric generalized anxiety disorder: epidemiology, diagnosis and management. Parental age and risk of autism spectrum disorders in a Finnish national birth cohort. Journal of Autism and Dev Disord 2013; in press Lindberg T, Wadsby M. Psychiatric and somatic health in relation to experience of parental divorce in childhood. International Journal of Social Psychiatry 2010 Sep 17 [Epub ahead of print] McCleery J, Allman E, Carver L, Dobkins K. Abnormal magnocellular pathway visual processing in infants at risk for autism. Altered white matter fractional anisotropy and social impairment in children with autism spectrum disorder. Brain Research 2010 Sept 18 [Epub ahead of print] Ptacek R. Attention deficit hyperactivity disorder and eating disorders. An evaluation of social skills in children with and without prenatal alcohol exposure. Developmental trajectories of child to adolescent externalizing behavior and adult DSM-IV disorder: results of a 24 year longitudinal study. Increased putamen and callosal motor suregion in treatment-naïve boys with Tourette syndrome indicates changes in the bihemispheric motor network. Journal of Child Psychology and Psychiatry and Allied Disciplines 1999; 40: 19-55. Sawyer M, Kosky R, Graetz B, Arney F, Zubrick S, Baghurst P. The National survey of mental health and wellbeing: the child and adolescent component. Australian and New Zealand Journal of Psychiatry 2000; 34:214-220. Brain hyperconnectivity in children with autism and its links to social deficits. From Child to adult: The Dunedin multidisciplinary health and development study. The genetics of child psychiatric disorders: focus on autism and Tourette syndrome. Refining the attention deficit hyperactivity disorder phenotype for molecular genetic studies. Molecular Psychiatry 2006; May 16; [Epub ahead of print]. Psychosis and autism: magnetic resonance imaging study of brain anatomy. Individual variation and longitudinal pattern of genome-wide DNA methylation from birth to the first two years of life. Child abuse and epigenetic mechanisms of disease risk. American Journal of Preventive Medicine 2013; 44:101-107. Use of ADHD drugs in the Nordic countries: a population-based comparison study. FEAR AND ANXIETY Introduction “It remains unclear whether anxiety states are to be better conceptualized as several putatively distinct diagnostic entities or as one broadly conceived syndrome within which there are no clear boundaries between various manifestations of anxiety” Vladan Starcevic (2006). Applies to the total organism, it refers to a state of readiness for activity, and involves increased sensory excitability, muscular tone and sympathetic and endocrine activity. Anxiety Most non-medical dictionaries define anxiety in this manner: “a feeling of worry, nervousness, or unease about something with an uncertain outcome” Non-medical synonyms for anxiety include “worry”. This is consistent with medical definitions: “Anxiety is a general term for several disorders that cause nervousness, fear, apprehension, and worrying. In earlier textbooks anxiety disorders were conceptualized as requiring two sets of symptoms - cognitive (worry) and somatic (tremor, sweating, palpitations, etc. This continues to be the case with the current International Classification of Disorders (ICD 10). However, in the DSM5, somatic symptoms in the form of those mentioned above, need not be present. Normal anxiety Normal anxiety has been applied to states of arousal/anxiety which occur in everyday life, in response to stimuli. It has an adaptive role and is a signal to take action. In normal anxiety the assessment of the danger is appropriate and the action taken is effective. The healthy person who has lost her/his pay-packet will be anxious about paying outstanding bills. Experiencing occasional anxiety is a normal part of life (Mayo Clinic, 2015). Fear is generally regarded to be an extreme form of normal anxiety. If an intruder comes into the house, most healthy persons will be fearful. Pathological anxiety Pathological anxiety is diagnosed when there is excessive assessment of danger. The individual may be unable to make any response, or make an excessive protective response. The person with pathological anxiety may be so disabled that he/she is unable to conduct his/her usual duties, such as prepare a meal, or overestimate a danger and make maladaptive adjustments (the person who is unduly anxious about lifts will have to take the stairs). One perspective is that normal anxiety is a normal response to an abnormal situation (anxiety at being threatened by a mugger) and pathological anxiety is an abnormal response to a normal situation (anxiety at needing to leave the home). However, this is too sensible to be widely embraced. At the current time, the distinction between “normal” and “pathological” worry/anxiety is arbitrary and depends on frequency and degree of arousal. Stress Stress refers to external stimuli to which there is need to adapt. In a stressful situation there may be a number of separate stressors. Stress is also used as a term to describe the state of being when subjected to stress (under stress; feeling stressed). It is unclear whether there is a difference between “feeling stressed” and “feeling anxious”. Yerkes-Dodson law (1908) has face validity in everyday life. This “law” describes a relationship between arousal and performance. As arousal increases so performance increases/improves, to a certain point, beyond which, as arousal continues to increase, performance deteriorates. Sports coaches say that when the spots-person does not feel some pre-games “nerves/tension” they do not perform at their best.
PD conjunction with a COMT inhibitor to enhance its dura- can also be associated with features that do not respond to tion of effect and thereby improve motor response and re- levodopa and can themselves be a major source of disability duce the risk of the drug inducing pulsatile stimulation of to the patient purchase chloramphenicol 250mg line. These include dementia chloramphenicol 500mg low cost, autonomic dysfunc- the dopamine receptor (see COMT Inhibitors purchase chloramphenicol 500 mg without prescription, below). Finally, there has been some concern that despite its Dopamine agonists are a group of drugs that act directly on many benefits, levodopa might accelerate neuronal degener- dopaminergic receptors. Historically, they have been used as ation through the oxidizing species generated through its adjuncts to levodopa in the treatment of PD since the 1970s oxidative metabolism. In particular, levodopa is oxidized by (61) and offer several theoretical advantages over levodopa MAO to form peroxides, which can combine with iron to (62): (a) They do not depend on enzymatic conversion for generate the cytotoxic hydroxyl radical (56). It is less clear that levodopa induces advanced stages of PD, at which time presynaptic dopamine toxicity in animal models, where it has been shown to in- neurons and terminals are largely degenerated. Levodopa has not been shown to induce damage (c) Most marketed dopamine agonists have longer half-lives to dopamine neurons in normal animals or humans, but and longer durations of action than levodopa. This may the situation may be different in PD, where the SNc is in permit more continuous (less pulsatile) stimulation of dopa- a state of oxidant stress and defense mechanisms are com- mine receptors than occurs with levodopa therapy. A recent consensus conference concluded that fore, there has been interest in the potential of this class of although the possibility that levodopa might be toxic in PD drug to reduce the risk of developing levodopa-related has not been excluded, there was no reason to withhold the motor complications (62). Long-acting formulations of both of these provide neuroprotective effects in PD (65). Lisuride, piribedil, and apomorphine treated primates demonstrate that bromocriptine and ropi- are other dopamine agonists that are available in some coun- nirole are associated with reduced frequency and severity of tries but not the United States. All dopamine agonists that dyskinesia compared to levodopa, even though all groups are marketed for the treatment of PD stimulate the D2 provide comparable behavioral effects (76,77). These data receptor, which is thought to underlie their antiparkinso- suggest that starting treatment for PD patients with a long- nian effects. Dopamine and apomorphine stimulate both acting dopamine agonist rather than levodopa might reduce D1 and D2 receptors. Pergolide is also a weak agonist and the risk of developing motor complications. However, until bromocriptine a weak antagonist of the D1 receptor. The recently dopamine agonists have not been well studied in role of D1 receptor activation or inhibition in PD is not early PD. There are now prospective double-blind con- known, although there is some suggestion that stimulation trolled studies demonstrating that both pramipexole and of both D1 and D2 receptors provides enhanced motor ropinirole provide improvement in measures of motor func- responses. Bromocriptine, pergolide, ropinirole, and prami- tions and activities of daily living (ADL) in otherwise un- pexole have plasma half-lives of 6 to 15 hours, whereas treated PD patients that are superior to placebo (78,79), cabergoline has a much longer elimination half-life of 63 and almost as good as levodopa (30,31). This contrasts with the plasma half-life of levo- tients can be maintained on dopamine agonist monotherapy dopa, which is 60 to 90 minutes. More importantly, it has now been established in prospec- tive double-blind long-term studies that PD patients ran- Dopamine Agonists in Patients with Advanced domized to initiate therapy with a dopamine agonist (ropi- PD nirole or pramipexole), supplemented with levodopa if necessary, have significantly fewer motor complications Since their introduction in the mid-1970s, dopamine ago- than patients randomized to begin therapy with levodopa nists have primarily been used as adjuncts to levodopa in PD alone (30,31). Reduced rates of both dyskinesia and motor patients with relatively advanced disease who have begun fluctuations were observed in the agonist-treated patients. As an adjunct to Measurements of motor function and ADL on the Unified levodopa, numerous prospective double-blind studies have Parkinson Disease Rating Scale (UPDRS) showed slight, demonstrated that dopamine agonists can significantly im- but significant, benefits in favor of levodopa-treated patients prove PD signs and symptoms, reduce dyskinesia and motor in both studies. This is difficult to explain, as patients in fluctuations, and reduce the need for levodopa therapy in both groups could have added open label levodopa to their comparison to placebo (67–73). Benefits have been ob- blinded treatment regimen if either the physician or the served with each of the currently approved dopamine ago- patient thought it was necessary. This raises the question nists and they are of approximately equal magnitude. Apo- as to whether the UPDRS fully captures all factors that morphine stimulates both D1 and D2 receptors. It has been used to provide a 'rescue effect' for ous dopaminergic stimulation, many authorities now rec- patients who turn 'off' and do not respond to their next ommend initiating symptomatic therapy for PD with a do- dose of levodopa (74). Some physicians have reported bene- pamine agonist, and reserving levodopa until such time as fits in advanced patients with complex motor complications the agonist can no longer provide satisfactory clinical con- with the use of continuous apomorphine (75). Others feel that the issue is still somewhat apomorphine must be administered parenterally, is associ- controversial and that physicians must choose between en- ated with cutaneous ulcerations at sites of entry, and is very hanced efficacy now versus delayed motor complications difficult to manage for both the physician and the patient. Our personal view is that the difference in motor and It therefore has relatively little role in routine practice. ADL scores between the agonist and levodopa groups is Despite the benefits obtained with dopamine agonists in negligible, whereas the difference in the rate of developing patients with advanced disease, they generally do not pro- motor complications is substantial and a much greater vide satisfactory control of motor function or motor compli- source of disability for the patient and frequently necessi- cations, and sooner or later alternate therapies must be tates surgical intervention as the only means of providing sought. To partially counter this effect, levodopa is rou- still favor the use of levodopa as the initial agent in patients tinely prescribed in combination with an inhibitor of with cognitive impairment or who are elderly. AADC that does not cross the blood–brain barrier and blocks the peripheral decarboxylation of levodopa into do- pamine. This combination reduces peripheral dopaminergic Adverse Effects of Dopamine Agonists side effects associated with the administration of levodopa The acute side effects of dopamine agonists are similar to alone, and increases the amount of levodopa that is available those observed with levodopa and include nausea, vomiting, to access the brain. However, even in the presence of a and postural hypotension (84). These side effects tend to decarboxylase inhibitor, the bulk of levodopa is still metabo- occur when treatment is initiated and abate over days or lized by COMT and only 10% of a given dose is transported weeks as tolerance develops. Introducing the agonist at a into the brain (17,89). Two new drugs that inhibit COMT, low dose, and slowly titrating to the desired effect reduces tolcapone (Tasmar) and entacapone (Comtan), have re- the probability that they will occur. Dopamine agonists can cently been introduced to the market as an adjunct to levo- acutely cause or intensify dyskinesias, but in the long term dopa therapy. Both drugs inhibit COMT in the periphery, they have the potential to lessen dyskinesias and motor fluc- although tolcapone has mild central effects as well. Entaca- tuations because of their long duration of action (see above). The ergot-derived dopamine ag- reach peak plasma concentration (Tmax) and effects are seen onists, bromocriptine, pergolide, and cabergoline, may have with both immediate and controlled release formulations ergot-related side effects including pleuropulmonary and (90–93). COMT inhibitors thus modulate peak and trough retroperitoneal fibrosis, erythromyalgia, and digital vaso- plasma levodopa concentrations, leading to a smoother spasm, although these are rare (84). The newer non-ergot plasma curve with reduced fluctuations in levodopa level dopamine agonists are less likely to induce these problems, (94). These pharmacokinetic effects have been shown to although there is anecdotal suggestion that they may still translate into enhanced levodopa entry into the brain on occur. Dose-related sedation may occur with dopamine ago- positron emission tomography (PET) (95) and clinical ben- nists (69,78), as with other dopaminergic agents including efits particularly for patients experiencing mild to moderate levodopa. More recently, sudden episodes of unintended motor fluctuations. Double-blind placebo-controlled clini- sleep while at the wheel of a motor vehicle have been de- cal trials in fluctuating PD patients demonstrate that scribed in PD patients and attributed to dopamine agonists COMT inhibitors increase the duration of beneficial effect (85). The episodes were termed 'sleep attacks' because they following a single levodopa dose (96). They also provide an occurred suddenly, although others have argued that there increase daily 'on' time of 15% to 25%, a decrease in is no evidence to support the concept of a sleep attack even 'off' time of 25% to 40%, improvement in UPDRS motor in narcolepsy. They have suggested that it is more likely scores, and a reduction in levodopa dose requirement of that these patients have unintended sleep episodes as a mani- 15% to 30% (97–100). Benefits with COMT inhibitors festation of excess daytime sedation due to nocturnal sleep have also been observed in nonfluctuating PD patients with disturbances that occur in 80% to 90% of PD patients and a stable response to levodopa. Two placebo-controlled trials to the sedative effect of dopaminergic medications (86). It showed improved motor scores and reduced levodopa dose is now apparent that these types of episodes can be associ- requirements in the group receiving the COMT inhibitor ated with all dopaminergic agents including levodopa (87). Physicians should be aware of the potential of dopaminergic There has also been interest in using COMT inhibitors agents to induce sleepiness, and that patients themselves from the time levodopa is first initiated in order to reduce may not be aware that they are sleepy. To detect excess the risk of developing motor complications (103). As de- sleepiness and to thereby introduce appropriate manage- scribed in the section on motor complications, laboratory ment strategies, it is necessary to employ sleep question- evidence supports the notion that treatment for PD patients naires such as the Epworth sleepiness scale, which inquires should be employed in such a way as to try and avoid pulsa- into the propensity to fall asleep and does not rely upon tile stimulation of dopamine receptors (51). Indeed, there subjective estimates of sleepiness (88). However, these patients Catechol O-Methyltransferase (COMT) eventually require levodopa, and when levodopa is adminis- Inhibitors tered the frequency of motor complications increases. It Orally ingested levodopa is massively transformed in the therefore has been postulated that administering levodopa periphery by two enzymatic systems—AADC and from the time it is first introduced with a COMT inhibitor 1802 Neuropsychopharmacology: The Fifth Generation of Progress to extend its half-life and deliver levodopa to the brain in data indicate that tolcapone is the more potent agent.
These findings led to the study of 81 patients chloramphenicol 500 mg discount, divided into three groups effective 250 mg chloramphenicol. One group received low doses of melato- nin in the afternoon and evening for 3 weeks cheap chloramphenicol 500mg otc. At this time of the year, he or she is probably begin- group received the same dosing regimen in the morning. By the way, another way to There is also a placebo group. Interestingly, the antidepres- cause a phase advance with respect to sleep time is to use sant response appears to be related to the amount of phase a dawn simulator set to start slowly increasing light intensity advance (49). Phase shifts owing to light relative to the sleep/wake cycle seems to be the optimal were of the same order of magnitude as phase shifts after amount (48). Although the duration can be reduced after 3 weeks of a divided dose of. Furthermore, any advance in sleep time We think it unlikely that a third week of treatment sub- should be minimized, since this will retard the antidepres- stantially increases the phase shift. This can be achieved while minimizing its soporific side effect, by using very low doses (. Hence, once 12 hours, we found phase shifts of the same order of magni- a patient has responded, the duration of bright light and/ tude as those obtained with bright light (97). Apparently, or the dose of melatonin can be reduced. Patients will need holding the light/dark cycle constant diminishes the phase- to be treated until the photoperiod lengthens in the spring. For the second day in Israel, follow the directions for crossing eight time zones. Melatonin can also be helpful in the treatment Jet Lag of jet lag. We are currently developing guidelines for the The first use of melatonin in humans was to treat jet lag optimal use of melatonin in the treatment of jet lag. There are surprisingly few studies in this area, however. For example, if you stances, only the sleep/wake cycle appeared to be entrained (103–105). We estimate that there are at least 100,000 totally blind people in the United States who have periodic insomnia. We have recently discovered a way to entrain most of these people (101,106). A dose of 10 mg given within an hour of preferred bedtime should in all likelihood eventually entrain most of them. Once the free-running clock of the blind person has been 'captured,' the maintenance dose can be decreased to as low as. Ongoing work in our labora- tory is investigating the possibility of moving the melatonin dose earlier, to 7 to 13 hours after habitual wake time, so as to provide a typical phase angle of entrainment. Therefore, it may be possible to entrain people initially with. Indeed, the only person who failed to entrain to the 10-mg dose had the longest free-running period of our group (24. Proposed times for when bright light exposure should occur and when bright light exposure should be avoided light response, such as the melatonin suppression test, which the first fewdays after transmeridional flight. For example, after we developed in sighted people (23,110–114)and has also a 2-hour west-to-east trip, bright light exposure should begin at been recommended for blind people (107). However, until dawn and should be (optimally) 2 hours in duration. In another example, after a 10-hour west-to-east trip, however, bright light we have ruled out entrainment by ocularly mediated light exposure should be avoided until 4 hours after sunrise and should in what are thought to be totally blind people, we do not occur (optimally) for 6 hours. Scheduled recommend the use of the melatonin suppression test, exposure to daylight: a potential strategy to reduce 'jet lag' fol- lowing transmeridian flight. Psychopharmacol Bull 1984;20: which we recently have come to think may risk desensitizing 566–568, with permission. The intrinsic period of one of these subjects was stud- ied in temporal isolation and was found to be 23. This should be of interest to those interested in else (24). We do not think that bright light has the same phenotyping sighted people for clock gene studies. Whether or not correcting the phase distur- The melatonin fad of a few years ago has stimulated a num- bance improves the remaining symptoms is not known at ber of scientists to make skeptical comments. There is no clinical evidence that melatonin is useful for anything other than phase shifting Melatonin in Young and Elderly People and sleep; however, some investigators have expressed skep- ticism even for these well-documented uses. However, we Although we might want to use lower doses of melatonin view this as a strength of the methodology: because the in young and elderly people, melatonin appears to be rea- subjects lived mainly at home, the findings can be more sonably safe in these populations as long as a physician is directly applied to real-life situations. Moreover, it is difficult to millions of people have been doing so for the past several imagine a systematic confound in the study owing to mela- years. However, we do not expect this to be a very up at night to take a placebo capsule causes phase shifts, if common effect of melatonin, given the fact that melatonin any, opposite to those of melatonin (Lewy, in preparation). Claustrat used a 3-hour and the fact that there is only a very slight seasonal rhythm intravenous infusion of melatonin, whereas our. This might explain why the intrave- Syndromes nous dose given in the evening produced more of a phase Appropriately timed bright light exposure and melatonin advance than the one given in the afternoon, in that the administration can be used to treat other circadian phase afternoon dose did not overlap with the endogenous melato- disorders. These include advanced sleep phase syndrome nin profile. Light ing effects increase as it is given earlier in the afternoon: treatment of these disorders has already been summarized even at this time, the. This issue is now moot, given the definitive findings of two independent groups (102,106). We agree with Czeisler that light is the most powerful phase-resetting agent. However, Czeisler thinks that light is an order of magnitude more powerful than light, whereas as indicated in the preceding (Table 129. In any event, melatonin is much more convenient than using light as a phase-resetting agent. Schematic diagram of some of the relationships zeitgeber. The jury is out as to the strength of the activity/ between nighttime melatonin production by the pineal gland, the light/dark cycle and the endogenous circadian pacemaker rest zeitgeber in humans. This second pathway duction appears to be critically involved in the regulation for entrainment by light is particularly significant during shifts of seasonal rhythms. However, this does not appear to be of the light/dark cycle. This function for melatonin is critically conveying the time of the year (primarily for seasonal breed- dependent on suppression of melatonin by bright light. The acute suppressant effect of light (23) regulates all overt circadian rhythms, including the nightly is important in truncating the endogenous melatonin pro- increase in pineal melatonin production. As mentioned in file, and humans have retained the suppressant effect of light the beginning of this chapter, melatonin feeds back onto but are not really seasonal breeders. Sufficiently bright light at ing, and that this difference might distinguish humans from the twilight transitions suppresses melatonin production, nonhuman primates. In other words, perhaps primates use causing the endogenous melatonin onset to occur later and melatonin either for telling the time of the year or the time the endogenous melatonin offset to occur earlier. In this way, the phase-shifting effect of Interestingly, activity is an effective zeitgeber in at least one light is augmented by an indirect effect of light acting on species of primates, which has a seasonal breeding cycle suppressing melatonin production. Simultaneously, the melatonin offset will occur 2 melatonin as one. The same thinking can be applied to geber, depending on whether or not melatonin is used for changes in bright exposure in the evening. Clearly, light is the major zeitgeber for entraining circa- Once again, there is no question that light is the primary dian rhythms. Does light have a specific antidepressant effect other than Optimal dosing of melatonin will depend on minimizing phase shifting? This may entail using a low-dose sustained-release other affective disorders?
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