Variations in [3H]imipramine and 5-HT2A but not [3H]paroxetine binding sites in suicide brains

Hippocampal neuropathology in suicide: Gaps in our knowledge and opportunities for a breakthrough

Suicide is a major global hazard. There is a need for increasing suicide awareness and effective and evidence-based interventions, targeting both suicidal ideation and conduct. However, anti-suicide pharmacological effects are unsatisfactory. The human hippocampus is vulnerable to neuropsychiatric damages and subsequently releases psychobiological signals. Human hippocampal studies of suicide completers have shown mechanistic changes in neurobiology, which, however, could not reflect the neuropathological 'fingerprints' of fatal suicide ideations and suicide attempts. In this review, we provide several leading theories of suicide, including the serotoninergic system, Wnt pathway and brain-derived neurotrophic factor/tropomyosin receptor kinase B signalling, and discuss the evidence for their roles in suicide and treatment. Moreover, the cognitive dysfunctions associated with suicide risk are discussed, as well as the novel evidence on cognitive therapies that decrease suicidal ideation. We highlight the need to apply multi-omics techniques (including single-nucleus RNA sequencing and mass spectrometry histochemistry) on hippocampal samples from donors who died by suicide or legal euthanasia, to clarify the aetiology of suicide and propose novel therapeutic strategies.

Gene expression related to serotonergic and glutamatergic neurotransmission is altered in the flinders sensitive line rat model of depression: Effect of ketamine

Major depressive disorder (MDD) is associated with dysfunctional serotonergic and glutamatergic neurotransmission, and the genetic animal model of depression Flinders Sensitive Line (FSL) rats display alterations in these systems relatively to their control strain Flinders Resistant Line (FRL). However, changes on transcript level related to serotonergic and glutamatergic signaling have only been sparsely studied in this model. The non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist ketamine has fast-onset antidepressant properties, and recent data implicate serotonergic neurotransmission in ketamine's antidepressant-like activities in rodents. Here, we investigated the transcript levels of 40 genes involved in serotonergic and glutamatergic neurotransmission in FSL and FRL rats in response to a single dose of ketamine (15 mg/kg; 90 min prior to euthanization). Using real-time quantitative polymerase chain reaction, we studied the effect of ketamine in the hippocampus, whereas strain differences were investigated in both hippocampus and frontal cortex. The expression of genes involved in serotonergic and glutamatergic neurotransmission were unaffected by a single dose of ketamine in the hippocampus. Relative to FRL rats, FSL rats displayed enhanced hippocampal transcript levels of 5-ht_2c , and P11, whereas the expression was reduced for 5-ht_2a , Nr2a, and Mglur2. In the frontal cortex, we found higher transcript levels of 5-ht_2c and Mglur2, whereas the expression of 5-ht_2a was reduced in FSL rats. Thus, ketamine is not associated with hippocampal alterations in serotonergic or glutamatergic genes at 90 min after an antidepressant dose. Furthermore, FSL rats display serotonergic and glutamatergic abnormalities on gene expression level that partly may resemble findings in MDD patients.

Gender, personality, and serotonin-2A receptor binding in healthy subjects

The vulnerability to mood disorders, impulsive-aggression, eating disorders, and suicidal behavior varies greatly with gender, and may reflect gender differences in central serotonergic function. We investigated the relationships of gender, mood, impulsivity, aggression and temperament to 5HT(2A) receptor binding in 21 healthy subjects using [18F]altanserin and PET neuroimaging. Binding potentials in pre-defined regions-of-interest (ROI) were calculated using the Logan graphical method, corrected for partial volume effects, and compared by gender with age co-varied. SPM analysis was used for voxel level comparisons. Altanserin binding (BP(P)) was greater in male than female subjects in the following nine ROIs: hippocampus (HIP) and Lt. HIP, lateral orbital frontal cortex (LOF) and Lt. LOF, left medial frontal cortex (Lt. MFC), left medial temporal cortex (Lt. MTC), left occipital cortex (Lt. OCC), thalamus (THL) and Lt. THL. Differences in Lt. HIP and Lt. MTL remained significant after Bonferroni correction. Gender differences were noted in the co-variation of psychological traits with BP(P) values in specific ROIs. Among males alone, aggression was negatively correlated with BP(P) values in Lt. LOF and Lt. MFC, and Suspiciousness positively correlated in LOF, Lt. LOF and Lt. MFC. Among female subjects alone, Negativism was positively correlated with BP(P) values in HIP, and Verbal Hostility in Lt. HIP. Altanserin binding in Lt. MTC was positively correlated with Persistence, with no significant gender effect. Gender differences in 5HT(2A) receptor function in specific ROIs may mediate expression of psychological characteristics such as aggression, suspiciousness and negativism. Future studies of 5HT(2A) receptor function and its relationship to behavior should control for gender.

Polymorphisms in the regulatory region of the human serotonin 5-HT2A receptor gene (HTR2A) influence gene expression

BACKGROUND

Genomic variation in the regulatory region of the serotonin (5-HT) 2A receptor gene (HTR2A) may contribute to altered levels of 5-HT2A receptor and to psychiatric disease.

METHODS

Frequency and linkage disequilibrium (LD) were determined for promoter single nucleotide polymorphisms (SNPs) -1438A/G, -1420C/T, and -783A/G in 156 subjects. Functional relevance of -1438A/G and -783A/G was assayed in vitro using a luciferase reporter assay and ex vivo using quantitative real time polymerase chain reaction in a set of human fibroblast cell lines.

RESULTS

Significant LD was observed between SNPs -1438A/G and -783A/G. In vitro assays showed no significant differences in promoter activity between the A- and G-allele of -1438 locus when expressed with the major alleles at -1420C/T and -783A/G; however, when the minor allele G at -783 was expressed with G-allele at -1438, promoter activity was significantly decreased. 5-HT2A receptor mRNA expression in human fibroblast cell lines confirmed that -783A/G polymorphism significantly modified the effects of -1438A/G SNP.

CONCLUSIONS

Our results demonstrate that SNP -783A/G modifies the effects of the major SNP -1438A/G. Future studies examining the association of -1438A/G polymorphism with diseases and 5-HT2A receptor expression analyses should account for this epistasis.

Prenatal stress in the rat alters 5-HT1A receptor binding in the ventral hippocampus

Exposure of a pregnant woman to physical and/or psychological stress might affect her offspring by promoting the development of various learning, behavioral and/or mood disorders in later life. The 5-HT1A and 5-HT2A receptors are prominently implicated in the modulation of anxiety and mood-related behaviors. Using a semi-quantitative radiolabel immunocytochemical analysis (immunobinding), we studied the effect of prenatal stress on binding of these two receptor subtypes in the hippocampus of 4-week-old male and female Fischer 344 rats. Levels of 5-HT1A immunobinding in the ventral hippocampus, which is primarily implicated in emotional processing, were significantly decreased in male offspring after prenatal stress. A trend towards a decrease was observed in the ventral hippocampus of females. In contrast, 5-HT1A immunobinding within the dorsal hippocampus, which is mainly related to learning and memory, was not affected by prenatal stress in offspring of either gender. Likewise, no significant differences between control and prenatally stressed rats were observed for levels of 5-HT2A immunobinding in either part of the hippocampus or gender. The observed reduction in hippocampal 5-HT1A receptor binding in male offspring after prenatal stress may have important consequences for adult anxiety- and depressive-like behavior.

Immunohistochemical study of the serotonergic neuronal system in an animal model of the mood disorder

The monoamine theory is one of the major hypotheses about the biological etiology of major depressive disorders. Recent pharmacological and postmortem investigations suggest that depressed patients have alterations in function of serotonergic neuronal system. However, the exact sites of alterations and the association between these alterations and the etiology of the disorder are still unclear. To elucidate these issues, we immunohistochemically examined vesicle monoamine transporter 2 (VMAT2), serotonin receptor type 1a (5HT1a), and serotonin transporter (5HTT) in the hippocampal region of reserpine-treated rats, an animal model of depression. The results showed more VMAT2-immunoreactive varicose fibers in the pyramidal cell layer of hippocampus and parahippocampal cortexes, and more intense 5HTT-immunoreactivity in the pyramidal cell layer and the area CA4 of hippocampus in the animal models compared to those of the controls. On the other hand, lower density of 5HT1a-immunoreactive deposits in the pyramidal cell layer of hippocampus and the parahippocampal cortex was observed in the animal models compared to those of the controls. These results suggest that a deficit of monoamines induces the alterations in the expression of the storage protein, the receptor and the transporter that are involved in the serotonergic neurotransmission in the hippocampal region. These alterations may underlie the changes of serotonergic system observed in the brains of patients with the depressive disorder.

Serotonin transport kinetics correlated between human platelets and brain synaptosomes

RATIONALE

Blood platelets have been used extensively as a model system for investigating the role of the serotonin transporter (SERT) in various psychiatric disorders, especially depression. However, to date, it is not known whether platelet serotonin (5-HT) transport would be related to that in brain.

OBJECTIVES

We examined 5-HT transport kinetics simultaneously in human blood platelets and human cortical brain synaptosomes to determine whether they were correlated.

METHODS

Blood platelets and synaptosomes were obtained from 25 patients undergoing epileptic surgery. Synaptosomes were obtained from normal margins of surgical neuropathology specimens of anterotemporal cortex.

RESULTS

Platelet SERT V(max) was significantly correlated with brain SERT V(max) on linear regression (r=0.58, p<0.005), after controlling for the confounding effects of gender (t=-2.4, p=0.025) and time of day (t=2.1, p<0.05). Consistent with previous observations, there was a negative correlation between the maximum velocity (V(max)) of platelet 5-HT transport and pO2 (r=-0.52, p<0.01). Females had a significantly higher pO2 than males (F=4.9, p<0.05). After accounting for gender differences, addition of pO2 did not add further strength to the regression, given the aforementioned gender differences in pO2. The correlation between unadjusted values for platelet vs brain SERT V(max) was r=0.3, p=0.06.

CONCLUSIONS

These results suggest that a relationship may exist between 5-HT transport in platelets and cortical synaptosomes, when appropriate controls for confounding factors are employed.

Decreased hippocampal 5-HT(2A) receptor binding in older depressed patients using [18F]altanserin positron emission tomography

Serotonin receptor changes have been associated with the pathophysiology and treatment of major depression. Only one other study has investigated serotonin receptor changes in older depressed patients. We used positron emission tomography (PET) and [18F]altanserin, a ligand with high affinity for the 5-HT(2A) receptor, to examine the relationship between 5-HT(2A) receptor density and depression. Depressed subjects (n = 16), age > 50 years, were recruited as part of a larger study. Older depressed subjects consisted of early-onset recurrent depression (EORD, n = 11) and late-onset depression (LOD, n = 5). An age-matched control group (n = 9) was also recruited. All subjects were right-handed, nonsmokers and antidepressant-free. Regions of interest were determined on a summed MPRAGE scan transformed into Talairach space and coregistered with the PET images. Depressed subjects had less hippocampal 5-HT(2A) receptor binding than controls (p = 0.05). No significant differences in receptor binding were found between EORD and LOD subjects. Depressed subjects not previously treated for depression (n = 6) had less hippocampal 5-HT(2A) receptor binding (p = 0.04) than previously treated subjects (n = 10). It may be that prior medication treatment provides a compensatory upregulation of the 5-HT(2A) receptor.

Decreased serotonin 5-HT2A receptor-stimulated phosphoinositide signaling in fibroblasts from melancholic depressed patients

Abnormalities in serotonin (5-HT) receptors and 5-HT receptor-mediated signal transduction systems have been widely reported in mood disorders. This study was intended to evaluate 5-HT(2A) receptor-coupled activation of phosphatidylinositol (PI) hydrolysis in subtypes of depression. Samples for fibroblast culture were obtained from patients with major depression with or without melancholia, and normal controls. Dose response curves were determined for 5-HT-induced PI hydrolysis. PI response was determined for bradykinin and l-alpha-lysophosphatidic acid (LPA), alternative Gq-coupled receptor agonists. [125I]LSD binding for 5-HT(2A) also was conducted. Finally, Western blot analysis was performed for phospholipase Cbeta1 (PLCbeta1) and Galpha(q/11) proteins. The maximum PI response observed with 5-HT was significantly lower in melancholics but not nonmelancholic patients relative to controls. Activation of PI hydrolysis by bradykinin and LPA was not reduced in melancholic vs melancholics and controls; responses to both agonists actually were increased in the melancholic group. [125I]LSD binding, PLCbeta1, and Galpha(q/11) protein levels did not differ between groups. The data raise the possibility that the reduced 5-HT(2A) receptor-induced PI hydrolysis is intrinsic to the receptor itself or its coupling to Gq protein, and is not related to altered availability of the 5-HT(2A) receptor, Gq or PLC.

Serotonergic platelet markers of suicidal behavior--do they really exist?

BACKGROUND

Abnormal changes in platelets used as peripheral markers of central serotonergic functions are said to be associated with suicidality and depression, but this association has not been supported by consistent findings.

AIM

This review based on selected, often quoted publications in this area focuses firstly, on obviously contradictory findings and, secondly, on potential methodological flaws explaining these discrepancies.

RESULTS

The platelet 5-HT transporter has been found to have an inconsistent association with suicidality; furthermore, the specificity of imipramine for the 5-HT transporter is most likely low, since the number of platelet impramine binding sites has not been reliably associated with platelet serotonin uptake (Vmax). Significant changes of platelet serotonin content in suicidal individuals, as described in various studies, are most likely due to washout periods that are too short to eliminate the effects of a previous drug intake, or, in violent suicide attempters, due to blood loss and dilution. Similar methodological shortcomings might account for an often-reported elevated number of platelet 5-HT(2) receptor binding sites in suicidal individuals. In many studies, the results have not been sufficiently controlled for drug effects on platelet 5-HT(2) receptors, and associations of platelet 5-HT(2) binding with selective classifications of suicidal behavior are often generalized as further evidence for an association of platelet 5-HT(2) receptors with 'suicidality'. Finally, changes in platelet MAO-B-activity in suicidal patients have not been reproducibly found, and the impact of smoking on MAO-B activity has not been controlled in any studies.

CONCLUSIONS

Methodological flaws such as small sample sizes, insufficient matching criteria for controls, use of inadequate ligands in binding experiments, nonconsideration of comorbidity etc. and considerable methodological differences between studies limit their validity and comparability. It does not seem possible, at present, to integrate published findings and concepts into a plausible biological model of suicidality.

Decreased hippocampal 5-HT2A receptor binding in major depressive disorder: in vivo measurement with [18F]altanserin positron emission tomography

BACKGROUND

Serotonin 5-HT(2A) receptors play an important role in the regulation of many functions that are disturbed in patients with major depressive disorder. Postmortem and positron emission tomography studies have reported both increased and decreased 5-HT(2A) receptor binding in different limbic and paralimbic regions.

METHODS

We conducted a quantitative 5-HT(2A) receptor binding study using positron emission tomography and [(18)F]altanserin of four regions hypothesized to have altered levels of 5-HT(2A) receptors in major depressive disorder. Using a four-compartment model, the 5-HT(2A) receptor distribution was estimated by calculating the regional [(18)F]altanserin k(3)/k(4) ratio in which k(3) is the rate of binding to the receptor and k(4) is the rate of dissociation from the receptor. Forty-six antidepressant-free patients with major depressive disorder and 29 healthy control subjects were enrolled.

RESULTS

5-HT(2A) receptor binding in the hippocampus was reduced by 29% in depressed subjects (p =.004). In other regions, 5-HT(2A) receptor binding was decreased (averaging 15%) but not significantly. Both groups had similar age-dependent decreases in 5-HT(2A) receptors throughout all brain regions.

CONCLUSIONS

Altered serotoninergic function in the hippocampus is likely involved in the disturbances of mood regulation in major depressive disorder, although the specific role of the 5-HT(2A) receptor changes is still unclear.

Altered platelet serotonin 5-HT2A receptor density but not second messenger inositol trisphosphate levels in drug-free schizophrenic patients

The 5-HT2A receptor binding parameters using [3H]ketanserine and its intracellular signal inositol 1,4,5 trisphosphate (IP3) concentrations were determined in platelets from schizophrenic patients so as to assess differences with respect to a control group and to a standardized antipsychotic drug treatment. Seventy-five antipsychotic-free patients with a DSM-IV diagnosis of paranoid schizophrenia were included in the study. Blood samples were collected before the onset of antipsychotic treatment (baseline values) and after 3 weeks of treatment. Antipsychotic-free schizophrenic patients showed significantly increased basal 5-HT2A densities in comparison to the control group, together with a significantly increase (23%) in the 5-HT2A binding density in those patients treated with risperidone. These changes could be attributed to an up-regulation of 5-HT2A receptors caused by previous treatment with antipsychotic drugs, which is consistent with the chronic effect of 5-HT2A antagonists to up-regulate the number of binding sites. With regard to second messenger IP3 concentrations, basal concentrations in schizophrenic patients were not significantly different from control values, nor was there any significant difference between basal vs. posttreatment values. These results are possibly related to failure of second messenger systems of 'translating' extracellular messages generated presynaptically into effective neurotransmitter signals in schizophrenic patients.

[3H]-ketanserin binding sites in different psychiatric disorders

The results of the present study showed the presence of a high-affinity and saturable binding of [3H]-ketanserin to frontal and parietal brain membranes obtained postmortem from bipolar, depressed, schizophrenic patients and normal controls. The human brain samples (60 frontal cortex and 51 parietal cortex), were donated by the Stanley Foundation Brain Collection. The overall data showed that normal controls, depressed and schizophrenic patients had a higher density in the frontal than in the parietal cortex, while bipolar patients did not show any difference. When the data were analysed according to the two hemispheres, some additional, intriguing observations were made: it emerged that [3H]-ketanserin binding sites did not show any difference in the two frontal cortices, while they were less represented in the right parietal cortex of normal and bipolar patients and more dense in schizophrenic patients. In conclusion, our study has demonstrated the presence of heterogenous alterations of [3H]-ketanserin binding sites in healthy controls and different psychiatric disorders that may be of help in a further elucidation of the specific role that 5-HT(2A) receptors may play in these disorders.

Serotonin transporter: a potential substrate in the biology of suicide

Suicide is a serious public health problem in the US, yet its neurobiological underpinnings are poorly understood. Suicide is highly correlated with depressive symptoms, and considerable evidence suggests that depression is associated with a relative deficiency in serotonergic neurotransmission. Serotonergic circuits also mediate impulsivity, a trait obviously relevant to suicide. These findings, taken together, suggest that alterations in the serotonergic system might contribute to suicidal behavior, serving as an impetus for researchers to scrutinize the serotonin transporter (SERT) as a potential substrate for the pathophysiology of suicide. Using post-mortem brain tissue, platelets, and DNA from suicide completers and attempters have not provided unequivocal evidence for a pre-eminent role for the SERT in the pathophysiology of suicide. This paper provides a review of several studies that have evaluated the role of the SERT in the pathophysiology of suicide.

Localized decrease in serotonin transporter-immunoreactive axons in the prefrontal cortex of depressed subjects committing suicide

A variety of postmortem brain studies and clinical investigations have provided evidence that reduced serotonin neurotransmission is associated with suicidal behavior and depression, and several serotonergic parameters have been found to be altered in the prefrontal cortex of suicide victims. However, the integrity of the serotonin innervation of the prefrontal cortex in mood disorders has not been directly investigated. The present study used immunocytochemical methods and an antibody against the serotonin transporter to examine the relative density of serotonin axons in the dorsolateral prefrontal cortex of suicide victims with a diagnosis of major depression. The mean total length of serotonin transporter-immunoreactive axons per unit area was unchanged in layers 2 and 4 of area 46 in the depressed suicide subjects compared to controls, but was significantly (P < 0.01) decreased by 24% in layer 6 in the depressed suicide group. The total length of serotonin transporter-positive axons in layer 6 was reduced in eight of the 12 depressed suicide subjects compared to their matched control subjects. These findings reveal that depressed subjects who have committed suicide exhibit a lamina-specific reduction in a marker of serotonin axons in the dorsolateral prefrontal cortex that may reflect an alteration in cortical serotonin neurotransmission.

Loss of the circadian variation of platelet [3H]imipramine binding in delusional compared with non-delusional endogenously depressed patients

BACKGROUND

The circadian variations of the serotonin reuptake sites were studied in 16 patients meeting DSM-IV criteria for major depression with melancholia, either with (n=8) or without (n=8) psychotic symptomatology.

METHOD

The [3H]imipramine binding sites were measured in platelet samples.

RESULTS

While no statistically significant difference was found between the morning (09:00 h) and evening (21:00 h) [3H]imipramine B(max) values in the control group, both the non-delusional and delusional melancholic patients showed higher evening than morning B(max) values, which were only statistically significant in the former. When both diagnostic groups were compared, the delusional patients showed significantly lower [3H]imipramine binding values than the non-delusional patients both in the morning and evening samples. Within the non-delusional depressed patients, those individuals with mood circadian variation, assessed by the 18th item of the HDRS, showed significantly lower B(max) values than those without mood variation. Lowest morning and evening B(max) values were noted in the delusional depressed group without mood variations.

CONCLUSIONS

These results suggest that delusional depressions might have a different neurobiological substrate with loss of chronobiological rhythms.

Different distributions of the 5-HT reuptake complex and the postsynaptic 5-HT(2A) receptors in Brodmann areas and brain hemispheres

The aim of the present study was to determine the distribution of the presynaptic 5-HT reuptake complex and the 5-HT(2A) receptors through Brodmann areas from two control subjects, together with the possible existence of laterality between both brain hemispheres. A left laterality was observed in the postsynaptic 5-HT(2A) binding sites, with significantly higher B(max) values in the left frontal and cingulate cortex. In frontal cortex, [3H]imipramine and [3H]paroxetine binding showed the highest B(max) values in areas 25, 10 and 11. In cingulate cortex, the highest [3H]imipramine and [3H]paroxetine B(max) values were noted in Brodmann area 33 followed by area 24, while postsynaptic 5-HT(2A) receptors were mainly distributed through Brodmann areas 23 and 29. In temporal cortex, the highest [3H]imipramine and [3H]paroxetine B(max) was noted in Brodmann areas 28 and 34, followed by areas 35 and 38. All Brodmann areas from parietal cortex (1, 2, 3, 4, 5, 6, 7, 39, 40 and 43) showed similar presynaptic and postsynaptic binding values. In occipital cortex no differences were observed with regard to the brain hemisphere or to the Brodmann area (17, 18 and 19). These results suggest the need to carefully define the brain hemisphere and the Brodmann areas studied, as well to avoid comparisons between studies including different Brodmann areas or brain hemispheres.

Decreased platelet [3H]paroxetine binding sites in suicide attempters

Research to date would suggest the possible involvement of the serotonin (5-HT) system in the pathophysiology of suicide. With this study, we aimed to investigate the platelet 5-HT transporter, by means of the specific binding of tritiated paroxetine ([3H]Par), in a sample of 20 suicide attempters recruited at a first-aid service, as compared with healthy control subjects and psychiatric patients with no current or previous history of suicide attempt. The results, showing a decreased number of [3H]Par binding sites in suicide attempters, would suggest the involvement of the presynaptic 5-HT transporter in self-aggressive behavior.

Altered 5-HT(2A) binding sites and second messenger inositol trisphosphate (IP(3)) levels in hippocampus but not in frontal cortex from depressed suicide victims

The binding parameters of 5-HT(2A) and levels of its second messenger, 1,4,5-trisphosphate (IP(3)), were simultaneously studied in frontal cortex and hippocampus from the brains of 18 control subjects and 18 depressed suicide victims. All suicides met DSM-III-R criteria for depressive symptoms, suffered a violent death and had not taken any antidepressant drugs for at least 6 months prior to death. A significant decrease in the number of 5-HT(2A) binding sites (154+/-22 vs. 254+/-36 fmol/mg), together with a significantly lower apparent affinity constant (1.02+/- 0.08 vs. 1. 36+/-0.09 nM), was detected in hippocampus but not in frontal cortex from the depressed suicides compared to the control subjects. Furthermore, IP(3) concentrations were significantly increased in hippocampus (3.2+/-0.3 vs. 2.1+/-0.3 pmol/g) but not in frontal cortex (1.3+/-0.3 vs. 2.7+/-0.5 pmol/g) from the suicide victims. The reported results may indicate a significant hypersensitivity of the 5-HT(2A) postsynaptic receptor located in the hippocampus from depressed suicide victims, giving rise to an enhancement of its intracellular signaling system with higher IP(3) production.

The ultimate resignation: suicide and search activity

This paper presents an integrative approach to suicidal behavior in terms of search activity concept. Search activity concept displays a broad and holistic approach to behavior, adaptation to environment, body resistance, brain amine metabolism, and REM-sleep functions. Search activity is defined as activity that is oriented to change the situation (or at least the subject's attitude to it) in the absence of a precise prediction of the outcome of such activity, but taking into consideration outcomes at all previous stages of activity. According to the proposed hypothesis, renunciation of search (a state opposed to search activity) leads to a feeling of helplessness, problem-solution deficits, inefficient coping, dreams that represent renunciation of search, and a drop in the activity of amines. All these factors further exacerbate the state of renunciation of search and elevate suicidal risk. In addition, the remnants of search activity are misdirected to self-defeating behaviors that increase mental pain and contribute to renunciation of search. This hypothesis integrates findings from a number of fields of study of suicidal behavior, resolves some paradoxes, suggests new lines of research, and raises suggestions for assessment and treatment of suicidal behavior.

Possible association of the short allele of the serotonin transporter promoter gene polymorphism (5-HTTLPR) with violent suicide

There is abundant evidence that the serotonin (5-HT) system is modulating mood and several behavioural traits and that disturbances in the regulation of this system can be associated with severe behavioural malfunctions, as aggressive implusive and suicidal behaviour.1 Recently a functional polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) was identified2 and the presence of one or two short alleles was associated with anxiety-related personality traits3 and several psychiatric disturbances, such as affective disorder4 or severe alcohol dependence.5 With respect to the importance of the 5-HT transporter in serotonergic transmission, we have genotyped the DNA of 58 Caucasian suicide victims (with unknown psychiatric diagnoses) and 110 healthy controls for the biallelic functional polymorphism in the 5-HTTLPR. We found a highly significant increased frequency of suicide victims being carriers of one or two short alleles (Fisher's Exact Test, two sided, P = 0.0003), which suggests that a genetically altered protein function within the serotonergic pathway might be involved in suicidality, independently from the clinical diagnosis.

Prediction of antidepressant effects of sleep deprivation by metabolic rates in the ventral anterior cingulate and medial prefrontal cortex

OBJECTIVE

Sleep deprivation has been shown to have an antidepressant benefit in a subgroup of depressed patients. Functional imaging studies by the authors and others have suggested that patients with elevated metabolic rates in the anterior cingulate gyrus at baseline are more likely to respond to either sleep deprivation or antidepressant medications than patients with normal metabolic rates. The authors extend their earlier work in a larger group of patients and explore additional brain areas with statistical probability mapping.

METHOD

Thirty-six patients with unipolar depression and 26 normal volunteers were studied with positron emission tomography before and after sleep deprivation. Response to sleep deprivation was defined as a 40% or larger decrease in total scores on the Hamilton Depression Rating Scale.

RESULTS

One-third of the depressed patients had a significant response to sleep deprivation. Responders had higher relative metabolic rates in the medial prefrontal cortex, ventral anterior cingulate, and posterior subcallosal gyrus at baseline than depressed patients who did not respond to sleep deprivation and normal volunteers. Lower Hamilton depression scores correlated significantly with lower metabolic rates in the left medial prefrontal cortex. After sleep deprivation, significant decreases in metabolic rates occurred in the medial prefrontal cortex and frontal pole in the patients who responded positively to sleep deprivation.

CONCLUSIONS

High pretreatment metabolic rates and decreases in metabolic rates after treatment in the medial prefrontal cortex may characterize a subgroup of depressed patients who improve following sleep deprivation and, perhaps, other antidepressant treatments.

Altered [3H]imipramine and 5-HT2 but not [3H]paroxetine binding sites in platelets from depressed patients

BACKGROUND

Serotonergic system alterations were studied in 51 depressed patients classified according to DSM-III-R criteria for major depression with melancholia compared to 31 healthy controls.

METHOD

[3H]Imipramine and [3H]paroxetine binding sites and the 5HT2 receptor were simultaneously determined in blood platelet membranes.

RESULTS

A significantly lower maximum binding in [3H]imipramine binding was observed in depressed patients compared to controls (1134+/-74 vs. 1712+/-106 fmol/mg protein, P<0.0001) without changes in the equilibrium dissociation constant (1.10+0.05 vs. 1.25-/+0.09 nM). [3H]Paroxetine binding did not differ between the two groups (Bmax, 1441+/-55 vs. 1280+/-81 fmol/mg protein; Kd, 0.060+/-0.002 vs. 0.062+/-0.002 nM). The K(d) value of 5HT2 binding was lower in depressed patients than controls (0.95+/-0.04 vs. 1.15+/-0.09 nM, P<0.039) without changes in maximum binding (140+/-11 vs. 127+/-14 fmol/mg protein).

CONCLUSIONS

Taken together, these results suggest that [3H]imipramine and 5HT2 receptors may be good biological markers for serotonergic dysfunction in depressive disorders.