Increased serotonin-2 binding sites in frontal cortex of suicide victims

Platelet serotonin-2 receptor binding sites in depression and suicide

In order to examine the role of serotonin-2 (5HT2) receptors in depression and suicide, we determined 5HT2 receptors using 125I-lysergic acid diethylamide (LSD) as the binding ligand in platelets obtained from 20 normal control and 23 drug-free depressed patients. Our results indicate significantly increased 125I-LSD binding sites (Bmax) in the platelets of depressed patients compared with normal control subjects. We also observed that a subgroup of depressed patients with a recent history of suicide attempts or suicidal ideation had significantly higher 5HT2 binding sites as compared with nonsuicidal depressed patients and normal controls. There were no significant differences in the apparent dissociation constant (Kd) values in the platelets of depressed patients compared with normal control subjects. To examine if the baseline 5HT2 receptors are related to either the severity of illness or treatment response, we determined the relationships of the baseline Bmax and Kd with baseline Hamilton Depression Rating Scale (HDRS) and Brief Psychiatric Rating Scale (BPRS) scores and change in scores after treatment. We found no significant correlation between baseline Bmax and Kd with the baseline HDRS or BPRS scores or change in these scores after psychoactive drug treatment. These results thus indicate increased platelet 5HT2 receptors in depression, but much more so in depressed patients with suicidal ideation or attempts.

A method for the in vivo investigation of the serotonergic 5-HT2 receptors in the human cerebral cortex using positron emission tomography and 18F-labeled setoperone

Following previous validation in baboons, we have studied the characteristics of [18F]setoperone as a radioligand for investigating serotonergic 5-hydroxytryptamine2 (5-HT2) receptors in the normal, unmedicated human brain with positron emission tomography (PET); subjects orally pretreated with therapeutic amounts of ketanserin, sulpiride, or prazosin were also studied to evaluate the specificity and sensitivity of [18F]setoperone brain specific binding. In controls (n = 10), the tracer showed a clear-cut retention in both frontal cortex and striatum (known to contain a high density of 5-HT2 receptors) relative to cerebellum (known to be devoid of 5-HT2 receptors). In the seven young controls (20-39 years old), the frontal cortex/cerebellum and striatum/cerebellum ratios increased during the first hour to reach similar values of 2.53 +/- 0.12 and 2.38 +/- 0.11 (mean +/- SEM), respectively, and were essentially stable during the second hour. Pretreatment with ketanserin (a 5-HT2 blocker) significantly reduced the frontal cortex/cerebellum ratio to 0.7-1.0 at 65 min, whereas the striatum/cerebellum ratio was significantly, but only partially, reduced. During sulpiride treatment (a D2 blocker), the frontal cortex/cerebellum ratio was not altered, whereas the striatum/cerebellum ratio was significantly, but only partially, reduced. With prazosin pretreatment (an alpha 1-adrenergic blocker), neither the frontal cortex/cerebellum nor the striatum/cerebellum ratio was modified. These data in humans with PET demonstrate that [18F]setoperone labels with high sensitivity and selectivity 5-HT2 receptors in the frontal cortex; in striata, however, binding is to both 5-HT2 and D2 receptors. The deproteinated-to-whole plasma radio-activity concentration ratio increased with time following injection. The mean percentage of intact [18F]setoperone, in deproteinated plasma, was 82, 74, 53, 45, 30, and 22% at 5, 10, 20, 30, 60, and 110 min following injection, respectively. These data indicate that [18F]setoperone (a) is significantly bound to plasma proteins and (b) is significantly metabolized into several labeled metabolites that are much more hydrophilic than setoperone and, hence, presumably do not cross the blood-brain barrier. These results suggest the suitability of [18F]setoperone data for modeling of 5-HT2 receptor binding in brain.

5HT2 receptor changes in major depression

The 5HT2 receptor has been studied using quantitative tritium film autoradiography in the postmortem frontal cortex of 15 cases suffering from major depression and controls, matched for age, gender, postmortem delay, and storage time. In unmedicated depressives there was a significant increase in 5HT2 receptor binding over matched control values. Antidepressant-treated depressives dying while depressed had 5HT2 receptor densities not significantly different from control values. Depressives dying euthymic, (i.e., recovered) showed a marked reduction in 5HT2 receptor binding when compared with controls. A tentative hierarchy of 5HT2 receptors in affective states is proposed.

CSF 5-HIAA, serum cortisol, and age differentially predict vegetative and cognitive symptoms in depression

Prior studies have shown that both cerebrospinal fluid (CSF) concentrations of 5-hydroxyindolacetic acid (5-HIAA) and serum cortisol levels are related to overall symptom severity in depression. In the present study, 30 unmedicated inpatients meeting Research Diagnostic Criteria (RDC) criteria for depression participated in serum cortisol collection and a lumbar puncture for CSF. A multiple regression evaluated the ability of CSF 5-HIAA, serum cortisol, and age to predict cognitive and vegetative symptom clusters of the Hamilton Rating Scale for Depression. The multiple regression to predict the vegetative symptom cluster was highly significant overall (p = 0.002) and found that age and cortisol but not 5-HIAA predicted vegetative symptoms. The regression to predict the cognitive cluster narrowly missed overall significance (p = 0.06). Both CSF 5-HIAA and serum cortisol predicted cognitive symptoms and 5-HIAA predicted the cognitive cluster more strongly than cortisol. Age did not predict cognitive symptoms. The results suggest a dissociation between serum cortisol levels and CSF 5-HIAA in predicting vegetative and cognitive symptom clusters in depression.

Autoradiographic analysis of [3H]ketanserin binding in the human brain postmortem: effect of suicide

In vitro quantitative autoradiography of 5-HT2 receptors, using [3H]ketanserin as a ligand, was performed on 24 human brains postmortem. Twelve brains were donated by suicide victims and 12 by matched controls. We found a characteristic decline in 5-HT2 receptors with age in several brain regions of the control group. This age dependence of ketanserin binding was not present in some of these brain regions of the suicide group. We also found a significant but anatomically selective reduction in the density of ketanserin binding sites in the young suicide group, compared to age-matched controls. This reduction was evident in portions of the prefrontal cortex. Homogenate binding assays on prefrontal cortex samples from a large group of suicides (n = 20) and controls (n = 23) showed that the difference in age dependence of ketanserin binding and the reduced binding in the young suicide group were explained by differences in Bmax values. No differences were observed in Kd. Sex, presence of alcohol and time from death to autopsy did not affect ketanserin binding, in our sample, as measured by either autoradiography or homogenate binding assay.

Serotonin 5-HT2 receptor binding on blood platelets as a state dependent marker in major affective disorder

Serotonin receptors of the 5-HT2 type were studied on platelet membranes from 15 patients suffering from major depression. Receptor binding and clinical state (assessed by the Hamilton and Beck rating scales) were examined in a drug free state upon admission and after 1 and 3 weeks of treatment with the antidepressant maprotiline (MPT). 5-HT2 receptor binding changed in correlation with changes in the clinical state of the patients as judged by the rating scales. Since most patients showed a clinical improvement, the patients as a group exhibited a significant decrease in binding concomitant with a drop in depression scores. However, in those patients in whom there was no clinical change or an increase in depression scores, 5-HT2 receptor binding did not change or increased, respectively, thus resulting in a significant correlation between clinical changes and changes in binding. These results support the use of 5-HT2 receptors on platelets in evaluating depression and its treatment.

Increased serotonin 5-HT2 receptor binding on blood platelets of suicidal men

In search of a physiological marker of depression and suicidal behavior, serotonin receptors of the 5-HT2 type were studied on platelet membranes from 19 control and 22 suicidal subjects. All were young, drug- and medication free men (18-21-years-old). 5-HT2 receptor binding was assayed using tritiated ketanserin at two concentrations. Receptor binding in the suicidal subjects was significantly higher than controls at both concentrations, the mean difference being around 50%. A similar difference between patients with major depressive disorder and matched controls has been observed previously. These findings support the use of 5-HT2 receptors on platelets as a research and diagnostic tool in depression and suicide.

A neuroendocrine study of 5HT function in depression: evidence for biological mechanisms of endogenous and psychosocial causation

To investigate whether depression is a consequence of disturbed function in 5HT systems, neuroendocrine responses to infusions of the 5HT precursor L-tryptophan (LTP) were studied in patients and controls. After an overnight fast and 60 min bed rest, a solution of LTP (10 g/l) was infused intravenously to a dose of 100 mg/kg over 30 min. Circulating growth hormone (GH), prolactin (PRL), cortisol and tryptophan concentrations were followed from 60 min pre-infusion to 60 min post-infusion. GH responses were attenuated in 23 major depressives (DSM-III) compared with 22 controls and were almost absent in endogenous depressives (New-castle criteria). PRL responses were normal in depressives who had lost more than 3 kg body weight but attenuated in those who had not. GH and PRL responses did not correlate with each other. Reduced basal tryptophan concentrations and more rapid tryptophan clearance were observed in the depressives, but there were no correlations with GH or PRL responses. However, basal cortisol concentrations, which were raised in depressives with chronic psychosocial difficulties, were strongly and inversely predictive of PRL responses in depressives and controls. Blunted GH and PRL responses to LTP appear to be distinct abnormalities in depression which may relate to two processes; (1), an endogenous mechanism indicated by reduced GH responses, and (2), an impairment in 5HT systems, indicated by blunted PRL responses and perhaps caused by raised circulating cortisol or reduced tryptophan concentrations.

5-HT1A Receptors in major depression

The 5-HT(1A) receptor has been studied using quantitative tritium film auto radiography in post-mortem frontal cortex of 15 cases suffering from major depression and controls matched for age, sex, post-mortem delay and storage time. 5-HT(1A) receptor binding in the depressive cohort was not significantly different from control values. No consistent effects of antidepressant medication or mental state at death were seen on the results.

Central serotonergic function in parasuicide

1. Central 5-HT is thought to be involved in neuronal inhibition and as such as a modulating influence in restraining the organism from responding to (e.g., especially adverse) stimuli. 2. Evidence for a role of central 5-HT in suicide arises from reduced concentrations of brain 5-HT or 5-HIAA in brain stem, reduced binding of [3-H]-IMI in brain tissue of frontal cortex/hypothalamus, and increased binding of radioligands to 5-HT-2 receptors in the frontal cortex. 3. Evidence for a role of central 5-HT in parasuicide arises from reduced concentrations of lumbar CSF 5-HIAA, reduced PRL responses to d,l-fenfluramine challenge, and increased CORT responses to 5-HTP challenge. 4. Since reduced central 5-HT activity appears to be consistently associated with impulsive aggression, it is possible that suicidal and parasuicidal acts in individuals with evidence of reduced central 5-HT activity are a manifestation of reduced impulse control. 5. Agents which enhance central 5-HT function and/or diminish the activity of neuronal systems involved in arousal (e.g. norepinephrine or dopamine) should be efficacious in reducing parasuicidal behavior.

Further evidence supporting the role of the serotonin system in suicidal behavior: a preliminary study of suicide attempters

The 3H-imipramine binding parameters (Bmax and Kd) were studied in platelets from female suicide attempters and from healthy volunteers. The Bmax was significantly lower among suicide attempters, with no modification of the Kd. These results provide support of the hypothesis that decreased serotonin function may play a role in suicidal behavior.

Serotonin function in affective disorders

The evidence indicating a specific abnormality of brain 5-HT function in depressed patients is reviewed. Biochemical studies have indicated that low plasma levels of tryptophan are unlikely to be the primary 'cause' of depression or of abnormal brain 5-HT function in depression. However, there may be a reduction of 5-HT synthesis or function in the brains of depressed patients and the uptake of 5-HT into platelets from depressed patients is consistently reduced. Neuroendocrine studies have suggested that various groups of depressed patients may exhibit different types of abnormal 5-HT-mediated responses. It is important to distinguish between the acute and chronic pharmacological effects of antidepressant treatment, which may account for the latency seen between onset of therapy and full clinical effect. Clinical studies have provided further evidence that 5-HT is implicated in the causation and treatment of depression, as both 5-HT precursors and selective inhibitors of 5-HT uptake are effective in the treatment of depression. Furthermore, inhibition of 5-HT synthesis can block the effect of antidepressant compounds. It is concluded that 5-HT function is decreased during depression, and that this carries important implications for the pharmacology of antidepressant drugs.

Distribution of serotonin 5-HT1C receptor mRNA in adult rat brain

Based on in situ hybridization histochemistry (ISHH), we describe the anatomical distribution of the serotonin 5-HT1C receptor mRNA. In addition to the very high levels in epithelial cells of the choroid plexus, 5-HT1C receptor mRNA is found throughout the limbic system, in catecholaminergic cells and in serotonergic neurons. Receptor transcripts are also present in the hypothalamus, numerous motor nuclei and the subthalamus. Our results correlate well with serotonin (5-HT) innervation and receptor binding. Receptor mRNA is present in many brain structures in addition to regions previously shown to have 5-HT1C receptor binding. The distribution of this receptor mRNA suggests that the 5-HT1C receptor may mediate a number of the central effects of 5-HT.

Does platelet serotonin receptor supersensitivity accompany endogenous depression?

In a population of drug-free bipolar and unipolar depressed women, it was found that the concentration of serotonin sufficient to induce half-maximal shape change velocity in platelets is significantly (p less than 0.001) lower (0.13 +/- 0.0.04 microM) than that of closely matched controls (0.532 +/- 0.1 microM). This platelet concentration becomes higher after 1-3 months of antidepressant treatment (0.47 +/- 0.16 microM). Possible mechanisms for this up- or down-regulation of platelet serotonin receptor responsiveness are discussed.

Biochemical aspects of suicidal behavior

1. In completed suicides, studies of brain regions and CSF indicate a dysfunction of the serotonergic system. 2. In suicidal patients, regardless of diagnoses, analyses of monoamine metabolites in lumbar CSF reveal decreased concentrations of the serotonin metabolite 5-HIAA. 3. In depressed suicidal patients, both low CSF 5-HIAA and low concentrations of the dopamine metabolite HVA are associated with suicidality. In addition, pathological dexamethasone-tests may indicate an increased suicide-risk in these patients. 4. In depressed patients, there is evidence that the association between CSF 5-HIAA and corticosteroids is in contrast to findings in depressed suicidal patients.

The psychological autopsy: methodological considerations for the study of adolescent suicide

The psychological autopsy has been employed to study risk factors for completed suicide for more than three decades. Despite a wide range in methods of approach to families and interview techniques, the studies show high compliance and remarkable consistency of results across a wide age range and diverse geographic samples. The convergent evidence is that the diagnostic information obtained is both reliable and valid, although it is likely that such an approach will be more specific than sensitive. Integration of data obtained through psychological autopsies with data obtained through biochemical, toxicological, and epidemiological approaches is likely to deepen our understanding of suicide. Successful completion of careful psychological autopsy studies should enable investigators to examine intensively patients who resemble suicide completers, thereby transcending the inherent limitations of this important first step in the investigation of suicide.

Increased serotonin2 (5-HT2) receptor binding as measured by 3H-lysergic acid diethylamide (3H-LSD) in the blood platelets of depressed patients

3H-Lysergic acid diethylamide (3H-LSD) binding, a putative measure of 5-HT2 receptor binding, was studied in the blood platelets of 29 depressed patients and 24 normal controls. The Bmax (maximum number of 3H-LSD binding sites) in the blood platelets of depressed patients was significantly greater than that of normal volunteers. This increase in Bmax was due to an increase in female depressed patients only. Bmax was significantly lower in female compared to male normal controls but there was no difference between male and female depressed patients. There was also no difference in Kd (an inverse measure of affinity of 3H-LSD binding to its sites) between normal controls and depressed patients. The correlations between Bmax of 3H-LSD binding and the Bmax of the 3H-imipramine binding site or the Vmax of 5-HT uptake sites were not significant. The role of serotonergic processes in the psychobiology of depression is discussed.

Ritanserin, a 5-HT2 receptor antagonist, activates midbrain dopamine neurons by blocking serotonergic inhibition

The effect of systemic administration of ritanserin (R 55667), a 5-hydroxytryptamine (5-HT2) receptor antagonist, on midbrain dopamine (DA) neurons was studied with single cell recording techniques in the chloral hydrate anesthetized male rat. Dopamine cells of the zona compacta, substantia nigra (ZC-SN) and the ventral tegmental area (VTA) were identified by established criteria. Ritanserin (0.5-2.0 mg/kg, IV) dose-dependently increased both the burst firing and firing rate of the midbrain DA neurons. These effects were prevented by endogenous 5-HT depletion through pretreatment with the 5-HT synthesis inhibitor para-chlorophenylalanine (PCPA, 300 mg/kg, IP, x3), which did not significantly alter the firing characteristics of the midbrain DA cells when given alone. These results suggest that 5-HT exerts an inhibitory control of midbrain DA cell activity mediated by 5-HT2 receptors. The stimulatory effect of ritanserin on midbrain DA systems might contribute to some of its clinical effects, such as improvement of mood, drive and motivation as well as its therapeutic actions in parkinsonism and type II schizophrenia.

Distinct morphologic classes of serotonergic axons in primates exhibit differential vulnerability to the psychotropic drug 3,4-methylenedioxymethamphetamine

Immunohistochemical methods were used to analyse the distribution and morphology of serotonergic axons in normal macaque monkeys and in monkeys given (+/-)3,4-methylenedioxymethamphetamine. In untreated monkeys, we observed two morphologic classes of serotonergic axon terminals, which differ in regional and laminar distribution. These two axon types, fine and beaded, correspond to the serotonergic axon types which have been described in the rat. In 3,4-methylenedioxymethamphetamine-treated monkeys, there is a profound loss of serotonergic axon terminals, yet some are consistently spared. The surviving axon terminals are nearly all of the beaded type; in contrast, fine serotonergic axons are markedly reduced in density. There are regional differences in the magnitude of denervation, which reflect differences in the distribution of these two types of serotonergic axons in controls. The present study demonstrates that 3,4-methylenedioxymethamphetamine has differential neurotoxic effects on fine and beaded serotonergic axons. These results indicate that in the primate there are two distinct classes of serotonergic axon terminals, which differ in morphology, distribution, and vulnerability to psychotropic drugs. We hypothesize that in the primate, as demonstrated in the rat, these two classes of serotonergic axon terminals may arise from different raphe nuclei. In both rodent and primate, the dorsal and median raphe nuclei give rise to parallel ascending serotonergic projections, which are likely to have different pharmacologic properties and functions.

Suicidal behavior, impulsiveness and serotonin

The authors review the accumulating evidence from preclinical, clinical and postmortem studies suggesting that abnormality in serotonin systems may be associated with both attempts at suicide and aggression towards others and inanimate objects. Although these behaviors are multidetermined they often involve poor impulse control, which may reflect low central serotonin turnover. The need for further studies of possible peripheral biological markers for suicidal and impulsive behavior is discussed.

Evidence for dual serotonergic projections to neocortex: axons from the dorsal and median raphe nuclei are differentially vulnerable to the neurotoxin p-chloroamphetamine (PCA)

Previous studies have shown that there are morphologically dissimilar serotonergic (5-HT) axon types in rat cerebral cortex which are differentially sensitive to the neurotoxic effects of certain psychotropic drugs: methylenedioxyamphetamines (MDA and MDMA) and p-chloroamphetamine (PCA) cause degeneration of fine 5-HT axon terminals in cortex, while sparing beaded axons. Moreover, a recent anterograde transport study suggests that fine and beaded 5-HT axons arise from the dorsal raphe (DR) and median raphe (MR) nuclei, respectively. These data led us to propose that the DR projection to neocortex is selectively vulnerable to the neurotoxic effects of PCA, while the MR projection is resistant; this hypothesis was tested in the present study by comparing retrograde axonal transport of the fluorescent tracer Fluoro-Gold in PCA-treated and control rats. Using this method, only axons that survive PCA treatment can take up and transport the injected label back to the cell bodies of origin, thus allowing us to determine which raphe-cortical projections remain intact after PCA. The results show that PCA administration produces a loss of fine 5-HT axon terminals in neocortex and a concomitant reduction in the number of retrogradely labeled neurons in the DR (77% decrease), when compared to controls. In contrast, beaded 5-HT axon terminals are spared and the number of labeled neurons in the MR remains unchanged after PCA. These results demonstrate that DR and MR projections to cortex are differentially vulnerable to PCA: fine axon terminals arise from neurons in the DR and are highly sensitive to the neurotoxic effects, whereas beaded axons from the MR are resistant. We therefore propose that there are two anatomically and functionally separate 5-HT projections to cortex having different (1) nuclei of origin, (2) axon morphology, (3) regional distributions, and (4) pharmacological properties. Since the mood-altering substances MDA, MDMA, and PCA act specifically upon 5-HT axon terminals from the dorsal raphe nucleus, DR neurons may be preferentially involved in the control of affective state.

The neuropathology of aminergic nuclei in Alzheimer's disease

Neuronal loss and the presence of neurofibrillary tangles (NFTs) within aminergic nuclei were examined in a series of patients with Alzheimer's disease (AD). Neuromelanin-containing neurons within the locus ceruleus and large nucleolus-containing neurons within the dorsal raphe nucleus and the central superior (raphe) nucleus were counted in 25 patients with AD and in 12 age-matched control subjects. Numbers of NFTs were quantified in the same regions. Counts were compared with clinical data, including psychiatric evaluations, available for 21 of the patients with AD. Within the locus ceruleus in the patients with AD, abnormalities were more severe at mid level than at caudal or rostral levels (p less than 0.01). Within the dorsal raphe nucleus, neuronal loss was most severe caudally (p less than 0.05). NFTs, but not neuronal loss, were demonstrated within the central superior nucleus. Neuronal and NFT counts did not correlate at individual levels; the relative severity of both pathological processes was consistent from level to level within nuclei but was less consistent between nuclei. Neuronal loss correlated inversely with age, particularly within the locus ceruleus. Duration of disease correlated inversely with counts of NFTs, particularly within the dorsal raphe nucleus, implying a correlation between NFT counts and rate of progression of disease as all but 3 patients had severe dementia. Significantly, patients with AD complicated by major depression had fewer neurons at the mid level of the locus ceruleus and at the rostral level of the central superior nucleus in comparison with nondepressed patients. There was a trend suggesting greater loss of neurons at all levels of the locus ceruleus and dorsal raphe nucleus in depressed individuals.

Cortical evoked potentials and clinical rating scales as measures of depressive illness

Relationships between clinical ratings and cortical evoked potentials were examined before and during antidepressant drug treatment in 32 patients with major depressive disorder (DSM-III). Clinical rating scales included Hamilton Rating Scale for Depression, Beck Depression Inventory, Present State Examination (PSE) and Newcastle Scale. Evoked potentials included contingent negative variation (CNV), post-imperative negative variation (PINV) and auditory evoked potential (AEP) There were close correlations between all rating scales, and factor analysis produced only one component, suggesting that the common variance between them related to severity of depression. CNV magnitude before treatment correlated negatively with severity of depression regardless of diagnostic category. Depressed patients had a prominent PINV which persisted during antidepressant treatment. The amplitude of late components (N1P2) of the AEP was reduced strikingly in patients with a history of suicide attempts.

Brain 5-HT2 receptor binding sites in depressed suicide victims

5-HT2 receptor binding sites were measured (by saturation binding of [3H]ketanserin) in brain tissue obtained at postmortem from 19 suicide victims with definite evidence of depression and 19 sex and age-matched control subjects. Five of the suicide victims were receiving antidepressant drugs prior to death; 13 suicide victims had not been prescribed antidepressant or other psychoactive drugs recently and none were found in their blood at postmortem. The number of serotonin-2 (5-HT2) binding sites in frontal, temporal and occipital cortex and amygdala did not differ significantly between the depressed suicide victims and controls, either in the total suicide group or in the antidepressant drug-free suicides. The number of 5-HT2 binding sites in the hippocampus did not differ from controls in the total suicide group but was significantly lower (by 23%) in the antidepressant-free suicide group. The affinity of [3H]ketanserin binding did not differ from controls in the antidepressant-free suicides but was lower (increased Kd) in those subjects receiving antidepressant drugs. No correlation was found between the time of death and storage of tissue or the duration of tissue storage prior to assay and the number or affinity of 5-HT2 binding sites. A significant negative correlation was found between age of the subject and the number of 5-HT2 binding sites in the frontal and occipital cortex. The present study of suicide victims with definite evidence of depression do not confirm previous studies of increased numbers of 5-HT2 binding sites in suicide victims and suggest that these previous findings may be related to factors other than depression.

Peripheral serotoninergic receptor sensitivity in senile dementia of the Alzheimer type

Platelet aggregation induced by 5-hydroxytryptamine (5-HT) was used as a measure of the functional responsiveness of peripheral 5-HT receptors in controls and drug-free patients suffering from senile dementia of Alzheimer type (SDAT). No significantly different aggregatory response (5-HT/ADP ratio) was noted between the two groups of subjects. If the receptor mediating this response is a 5-HT2 receptor, there is no evidence to suggest that the functional activity of this system is abnormal in SDAT.

Decrease of serotonin-S2 receptors in temporal cortex of patients with Parkinson's disease and progressive supranuclear palsy

The number of serotonin-S2 receptors was decreased in the temporal cortex of patients with Parkinson's disease and progressive supranuclear palsy (PSP). There was no significant modification of these receptors in the frontal cortex or in the hippocampus and putamen in both diseases. The decrease in number of receptors in PSP was unexpected, because the cerebral cortex is thought to be spared in this disease. There was no correlation between the decrease in number of serotonin-S2 receptors and the degree of dementia in Parkinson's disease, suggesting that these receptors are not directly involved in the deterioration of cognitive functions.

The neurobiology of aging: does it predispose to depression?

This review examines the various research approaches undertaken to investigate possible central nervous system correlates of major depressive illness and relates findings from these studies to the alterations in central nervous system and neuroendocrine function that normally accompany aging in humans. The topics reviewed include: epidemiology of depression and suicide in the elderly; monoamine theories of depression; neuroendocrine disturbances in depression; and imaging studies.

Serotonin 5-HT2 receptor binding on blood platelets--a peripheral marker for depression?

Several methods of platelet membrane preparation and binding conditions were screened in order to optimize the labeling of serotonergic 5-HT2 receptors on previously frozen human platelet membranes with tritiated ketanserin. Under optimal conditions, 5-HT2 receptors in normal subjects (5 males, 7 females, age range 21 to 71) have a Kd of 1.5 +/- 0.2 nM and a Bmax of 33.9 +/- 5.3 fmole/mg protein. In a group of patients with major depressive disorder exactly matched for age and sex with the normal control group, we find a significant increase in receptor density, to 66.8 +/- 11.4 fmole/mg, with no significant change in the affinity (2.3 +/- 0.5 nM). Four weeks of treatment with antidepressant drugs result in a significant decrease of Bmax, down to control levels (29.4 +/- 3.9). Thus, ketanserin can be used to monitor changes in platelet serotonin 5-HT2 receptors which may be a relevant marker for the state of depression.

Whole blood serotonin and plasma tryptophan using high-pressure liquid chromatography with electrochemical detection

Methods are detailed for whole blood serotonin (5-HT), equivalent to platelet 5-HT, and plasma tryptophan. These assays may be carried out on the same blood sample which need be no more than 1 ml, are rapid, and avoid the difficulties, such as protein precipitation and fluorophor formation, encountered in other methods. The linearity of the methods is extensive and allows for accurate measurement of low concentrations. Data are given for normal humans and for patients receiving psychiatric treatment for depression.

Assessment of suicide risk

Among the many clinical skills that psychiatrists must acquire, the ability to assess the risk of patients killing themselves is probably the most important and demanding. It is often a crucial factor when making clinical decisions, such as in the choice of treatments, when deciding whether admission to a psychiatric hospital is necessary and when implementing the Mental Health Act. This review first explores the problems in assessing suicide risk. Subsequently, the risks of suicide for patients with major psychiatric disorders and for particular clinical populations, including hospitalised patients and suicide attempters, are examined together with the findings from research investigations which can assist psychiatrists when making decisions about the risk of suicide.

Pitfalls in membrane binding sites studies in post-mortem human brain

A number of neurotransmitter receptor sites have been characterized biochemically in post-mortem human brain from normal subjects and in several neurological and psychiatric diseases. Such studies are valid, however, only when appropriate pre-mortem and post-mortem conditions are controlled. The effects of age, pre-mortem agonic conditions, drug therapy and post-mortem delay on the characteristics of five binding sites (alpha-1, alpha-2 and beta adrenergic receptors, 5HT-2 serotoninergic receptors, imipramine binding sites) were studied. Age related changes in receptor number were found. Pre-mortem anoxia and hypovolemia had no influence on receptor characteristics. The drugs administered before death, in particular neuroleptics, were found to affect binding to some receptors in post-mortem tissue. A post-mortem delay up to 24 hours after death had no effect on binding sites. Experimental strategies (single point values or saturation curves) were also compared.

Localization of serotonin 5-HT2 receptors in living human brain by positron emission tomography using N1-([11C]-methyl)-2-Br-LSD

N1-([11C]-Methyl)-2-Br-LSD ([11C]-MBL) has been developed as a positron emission tomography (PET) imaging agent for serotonin 5-HT2 receptors. In vitro receptor binding assays with nonradioactive MBL show high-affinity binding to serotonin 5-HT2 receptors (Ki = 0.5 nM), a secondary interaction of 8-fold lower affinity with dopamine D2 receptors, and low-affinity interactions with alpha 1-adrenergic as well as serotonin 5-HT1 receptors. Intravenous injection of [11C]-MBL in a baboon led to selective labeling of cortical regions that was markedly blocked by prior administration of ketanserin, a selective 5-HT2 receptor antagonist. Clinical trials with [11C]-MBL have been conducted in seven normal human volunteers, and the regional distribution of radioactivity in the brain was distinctly serotonergic. Labeling was highest in frontal, temporal, and parietal cortex with lower levels observed in caudate and putamen. The tracer rapidly washed from the cerebellum and the low levels of activity in this brain region were used to define nonspecific binding. The maximum specificity was reached between 30 and 60 minutes postinjection when frontal cortex to cerebellum ratios ranged from 1.7 for a 52-year-old male to 2.7 for a 30-year-old male. In agreement with previous studies, a trend towards lower ratios (lower serotonin 5-HT2 receptor levels) was observed in older volunteers. These studies indicate that [11C]-MBL is a selective radioligand that can be used to monitor serotonin 5-HT2 receptor densities in vivo in most regions of the human brain.

Biological suicide research: outcome and limitations

Empirical study of suicide began early in this century from the sociological (Durkheim 1951) and psychological (Freud 1956) perspective. A decade ago, a biological dimension was added, focusing on two major issues, i.e., are disturbances in brain functioning instrumental in the occurrence of suicidal behavior and/or do such disturbances increase the likelihood of suicidal behavior in an individual exposed to stressful events? Biological suicide research has developed as an offshoot of biological depression research. This is a logical development, as depression is a major precursor of both attempted (Weissman et al. 1973; van Praag 1982a) and completed (Guze and Robins 1970; Miles 1977) suicide. The major biochemical research targets are similar: monoamines and hormones. This paper will review the main findings in suicidal behavior, discuss the methodological shortcomings of this research, and indicate ways of avoiding them.