Serotonergic measures in suicide brain: the concentration of 5-HIAA, HVA, and tryptophan in frontal cortex of suicide victims

In Search for a Pathogenesis of Major Depression and Suicide-A Joint Investigation of Dopamine and Fiber Tract Anatomy Focusing on the Human Ventral Mesencephalic Tegmentum: Description of a Workflow

Major depressive disorder (MDD) is prevalent with a high subjective and socio-economic burden. Despite the effectiveness of classical treatment methods, 20-30% of patients stay treatment-resistant. Deep Brain Stimulation of the superolateral branch of the medial forebrain bundle is emerging as a clinical treatment. The stimulation region (ventral tegmental area, VTA), supported by experimental data, points to the role of dopaminergic (DA) transmission in disease pathology. This work sets out to develop a workflow that will allow the performance of analyses on midbrain DA-ergic neurons and projections in subjects who have committed suicide. Human midbrains were retrieved during autopsy, formalin-fixed, and scanned in a Bruker MRI scanner (7T). Sections were sliced, stained for tyrosine hydroxylase (TH), digitized, and integrated into the Montreal Neurological Institute (MNI) brain space together with a high-resolution fiber tract atlas. Subnuclei of the VTA region were identified. TH-positive neurons and fibers were semi-quantitatively evaluated. The study established a rigorous protocol allowing for parallel histological assessments and fiber tractographic analysis in a common space. Semi-quantitative readings are feasible and allow the detection of cell loss in VTA subnuclei. This work describes the intricate workflow and first results of an investigation of DA anatomy in VTA subnuclei in a growing naturalistic database.

Dopamine Function and Hypothalamic-Pituitary-Thyroid Axis Activity in Major Depressed Patients with Suicidal Behavior

Involvement of the dopaminergic (DA) and hypothalamic-pituitary-thyroid (HPT) systems in suicidal behavior is still poorly understood. We assessed multihormonal responses to apomorphine (APO; a short acting DA receptor agonist) and 8 AM and 11 PM protirelin (TRH) tests in 30 medication-free DSM-5 euthyroid major depressed inpatients with suicidal behavior disorder (SBD) (current, n = 14; in early remission, n = 16) and 18 healthy hospitalized control subjects (HCs). Compared to HCs, responses to APO and TRH tests were unaltered in SBDs in early remission. However, current SBDs exhibited increased APO-induced growth hormone (GH) and adrenocorticotropin (ACTH) stimulation, and reduced 11 PM thyrotropin (TSH) and ∆∆TSH values (difference between 11 PM and 8 AM TRH-TSH responses). In current SBDs, the association between high APO-GH concentrations and low ∆∆TSH values was more common in recent suicide attempters than in past suicide attempters. These preliminary results suggest that co-occurring alterations in the DA and HPT systems (i.e., DA receptor hyperresponsiveness associated with decreased hypothalamic TRH drive) may contribute to the pathophysiology of suicidal behavior. Conversely, normalization of DA and TRH functions might reflect a process of recovery from suicidality. Thus, our findings suggest that drugs targeting the DAergic and TRH systems could be relevant in suicide prevention.

Neurochemical and Behavioral Dysfunctions in Pesticide Exposed Farm Workers: A Clinical Outcome

The problem of pesticides is not new and its exposure to human due to indiscriminate use is largely associated with the health related problems including neurotoxicological alterations. High levels of pesticide residues and their metabolites in the dietary constituents, food materials, maternal blood, cord blood, placenta breast milk have been reported and linked to alterations in birth weight, crown heel length, head circumference, mid-arm circumference and ponderal index of the neonates. Epidemiological studies have suggested that exposure of pesticide to human could be a significant risk factor for neurological disorders, including Parkinson's disease, Alzheimer's disease and multiple sclerosis. Cholinergic and non-cholinergic dysfunctions in pesticide exposed population, especially in children have also been frequently reported in recent years. Developmental neurotoxicity is another concern in the area where pregnant are more prone towards its exposure and which results in the abnormalities in the fetus. In view of the increasing risk of human health through pesticide exposure, the present review has been focused on the studies pertaining to pesticide induced neurochemical alterations and associated behavioral abnormalities in farm workers which could establish a possible link between the its exposure and associated health hazards.

Toward a biosignature for suicide

OBJECTIVE

Suicide, a major cause of death worldwide, has distinct biological underpinnings. The authors review and synthesize the research literature on biomarkers of suicide, with the aim of using the findings of these studies to develop a coherent model for the biological diathesis for suicide.

METHOD

The authors examined studies covering a large range of neurobiological systems implicated in suicide. They provide succinct descriptions of each system to provide a context for interpreting the meaning of findings in suicide.

RESULTS

Several lines of evidence implicate dysregulation in stress response systems, especially the hypothalamic-pituitary-adrenal axis, as a diathesis for suicide. Additional findings related to neuroinflammatory indices, glutamatergic function, and neuronal plasticity at the cellular and circuitry level may reflect downstream effects of such dysregulation. Whether serotonergic abnormalities observed in individuals who have died by suicide are independent of stress response abnormalities is an unresolved question.

CONCLUSIONS

The most compelling biomarkers for suicide are linked to altered stress responses and their downstream effects, and to abnormalities in the serotonergic system. Studying these systems in parallel and in the same populations may elucidate the role of each and their interplay, possibly leading to identification of new treatment targets and biological predictors.

NEUROBIOLOGICAL ASPECTS OF SUICIDE AND SUICIDE ATTEMPTS IN BIPOLAR DISORDER

Suicide and bipolar disorder (BD) are challenging, complex, and intertwined areas of study in contemporary psychiatry. Indeed, BD is associated with the highest lifetime risk for suicide attempt and completion of all the psychiatric conditions. Given that several clinical risk factors for both suicide and BD have been well noted in the literature, exploring the neurobiological aspects of suicide in BD may provide insights into both preventive measures and future novel treatments. This review synthesizes findings regarding the neurobiological aspects of suicide and, when applicable, their link to BD. Neurochemical findings, genes/epigenetics, and potential molecular targets for current or future treatments are discussed. The role of endophenotypes and related proximal and distal risk factors underlying suicidal behavior are also explored. Lastly, we discuss the manner in which preclinical work on aggression and impulsivity may provide additional insights for the future development of novel treatments.

Biogenic Amines in Striatum of Rats that Had Been Treated with Ethanol, and Their Brains Later Stored in Different Temperatures

The purpose of this study was to investigate how ethanol pretreatment and storage temperatures of brain striatum affect levels of biogenic amines in this tissue. Adult Wistar male rats were injected with 25% ethanol (5.0 g/kg i.p.) while the control rats were administered i.p. with the same volume of saline. Two hours later the rats were decapitated, their brains removed, and the striatum separated. Each striatum was divided into three parts: one part was immediately frozen on dry ice and kept at -70 degrees C; a second fragment was kept in a household refrigerator (+4 degrees C); and the third fragment was kept at +22 degrees C. Twenty-four hours later, levels of DA, DOPAC, HVA, 3-MT, 5-HT, and 5-HIAA in the striatum were assayed by HPLC/ED. Immediately after decapitation; ethanol levels were assayed in the serum of ethanol-pretreated and saline-pretreated rats using gas chromatography. Our results indicate that levels of striatal DA, DOPAC, and HVA in saline-pretreated rats decreased significantly when the storage temperature of the striatum was raised from -70 degrees C, through +4 degrees C, to +22 degrees C, while levels of striatal 5-HT and 5-HIAA remained constant within the temperature range tested and levels of 3-MT fluctuated. In ethanol-pretreated rats, striatal levels of DOPAC, HVA, and 5-HIAA were increased in all three storage temperatures, while levels of DA, 5-HT, and 3-MT were decreased in those temperatures. Those decreases were most profound in striatal samples kept at +22 degrees C. We conclude that concern about possible interactions between drugs and biogenic amines should be exercised.

CSF biomarkers in suicide attempters--a principal component analysis

OBJECTIVE

The objective of the present study was to identify biological patterns (factors) among 20 cerebrospinal fluid (CSF) biomarkers in suicide attempters and subsequently analyse their association with suicidal behaviour.

METHOD

We measured kynurenic acid, orexin, homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), 3-methoxy-4-hydroxyphenylglycol, chemokines, matrix metalloproteases and cytokines in the CSF of 124 drug-free suicide attempters. Patients were evaluated for suicidality and psychiatric symptoms using well-defined psychiatric rating scales and followed-up regarding future suicide. We used principal component analysis to identify factors among the biological substances.

RESULTS

Four factors were extracted from the 20 biomarkers, explaining 52.4% of the total variance. Factors 1 and 2 were characterized by high loadings of chemokines and cytokines respectively. They were both associated with severe depressive symptoms. Factor 2 was also associated with a high suicidal intent. Factor 4 was characterized by strong loadings of the monoamine metabolites 5-HIAA and HVA, as well as orexin and interleukin-6. High scores on this factor were found in patients who performed a violent suicide attempt and in patients who subsequently completed suicide.

CONCLUSION

Our results suggest that specific combinations of CSF biomarkers may discriminate between types of suicidal behaviour and indicate increased risk for future suicide.

Binding of pramipexole to extrastriatal dopamine D2/D3 receptors in the human brain: a positron emission tomography study using 11C-FLB 457

The purpose of this study was to determine the binding sites of pramipexole in extrastriatal dopaminergic regions because its antidepressive effects have been speculated to occur by activating the dopamine D(2) receptor subfamily in extrastriatal areas. Dynamic positron emission tomography (PET) scanning using (11)C-FLB 457 for quantification of D(2)/D(3) receptor subtype was performed on 15 healthy volunteers. Each subject underwent two PET scans before and after receiving a single dose of pramipexole (0, 0.125, or 0.25 mg). The study demonstrated that pramipexole significantly binds to D(2)/D(3) receptors in the prefrontal cortex, amygdala, and medial and lateral thalamus at a dose of 0.25 mg. These regions have been indicated to have some relation to depression and may be part of the target sites where pramipexole exerts its antidepressive effects.

Extrastriatal D2 and striatal D2 receptors in depressive illness: pilot PET studies using [11C]FLB 457 and [11C]raclopride

BACKGROUND

Reduced dopaminergic function may occur in depressive disorders. In this paper the results of two pilot studies examining different aspects of the dopamine system in depression are presented. First, the binding of [(11)C]FLB 457 to extrastriatal D(2) receptors was measured in a group of depressed patients. Second, the hypothesis that selective serotonin reuptake inhibiting (SSRI) antidepressants affect the striatal binding of [(11)C]raclopride was tested.

METHODS

In the first study the binding of [(11)C]FLB 457 was compared between 7 people with depression and 7 healthy controls. In the second study the binding of [(11)C]raclopride to striatal D(2/3) receptors was compared between 8 people taking SSRI antidepressant medication and 8 healthy controls.

RESULTS

There was no difference in the binding of [(11)C]FLB 457 between the two groups. [(11)C]raclopride binding was reduced in the dorsal striatum of people taking antidepressants suggesting either that D(2/3) expression was reduced, or that dopamine release was increased, compared to untreated controls.

LIMITATIONS

The depressed patients were not severely depressed and were not matched for gender with controls. In the raclopride group the patients and controls were not matched by gender and were taking different SSRI antidepressants.

CONCLUSION

We found no support for the hypothesis that dopamine D(2) receptor expression is altered in extrastriatal brain regions in depression. SSRI antidepressants were associated with reduced [(11)C]raclopride binding in the dorsal striatum supporting the hypothesis that therapeutic effects of such drugs may, in part, be due to changes in the dopamine system.

Lower cerebrospinal fluid homovanillic acid levels in depressed suicide attempters

BACKGROUND

Studies suggest that the dopaminergic system is involved in the pathogenesis of major depression, Axis II disorders, and suicidal behavior. Depressed suicide attempters constitute a heterogenous group and important differences may exist between depressed suicide attempters with or without Axis II disorders. Therefore, we compared demographic and clinical parameters, and cerebrospinal fluid (CSF) homovanillic acid (HVA) levels in depressed suicide attempters without comorbid Axis II disorders, depressed non-attempters without comorbid Axis II disorders, and normal controls.

METHODS

Thirty-one depressed subjects with a history of a suicide attempt, 27 depressed subjects without a history of a suicide attempt, and 50 healthy controls were included in the study. Subjects with comorbid Axis II disorders were excluded. Demographic and clinical parameters, and CSF HVA levels were examined.

RESULTS

The two depressed groups did not differ with regard to depression, aggression, hopelessness, and total hostility scale scores. Depressed suicide attempters had higher current suicidal ideation scores compared to depressed non-attempters. Depressed suicide attempters had lower CSF HVA levels compared to depressed non-attempters (t = 4.4, df = 56, p < 0.0001) and to controls (t = -4.09, df = 79, p < 0.0001). There was no difference in CSF HVA levels between depressed non-attempters and controls (t < 1, df = 75, NS).

CONCLUSIONS

Dopaminergic abnormalities are associated with suicidality but not with depression. The variability in the rates of comorbid Axis II disorders and in the prevalence of suicide attempters in different patient populations may affect both clinical and biological results of studies of mood disorders.

Relapse in violent crime in relation to cerebrospinal fluid monoamine metabolites (5-HIAA, HVA and HMPG) in male forensic psychiatric patients convicted of murder: a 16-year follow-up

OBJECTIVE

Our purpose was to investigate if low levels of cerebrospinal fluid (CSF) monoamine metabolites of 5-HIAA, HVA and HMPG predict relapse in violent crimes.

METHOD

Relapse in crime and level of CSF monoamine metabolites (5-HIAA, HVA and HMPG) was studied in a group of 29 murderers. The follow-up was 16 years.

RESULTS

Fourteen of the 29 murderers were convicted of crime; nine of them committed violent crimes; one was convicted of a new murder. The differences in mean CSF monoamine metabolites were lower in subjects who relapsed into any type of crime, but only the difference in mean CSF HVA was statistically significant.

CONCLUSION

The risk to commit new murder is very small in males who earlier have been convicted of murder. Low levels of CSF HVA is associated with an increased risk for relapse in any type of crime.

Association of the -141C Del variant of the dopamine D2 receptor (DRD2) with positive family history and suicidality in German alcoholics

Several lines of evidence indicate an involvement of the dopaminergic system in alcoholism, withdrawal, suicidality, and attention-deficit hyperactivity disorder (ADHD). The functionally relevant -141C Ins/Del polymorphism located upstream to exon 1 in the 5'-region of the dopamine D2 receptor (DRD2) gene might be an interesting candidate gene. We investigated a sample of 1,126 well-characterized, primary chronic alcoholics of German descent according to a phenotype-genotype strategy, i.e., alcoholics suffering from severe withdrawal complications such as seizure or delirium, family history positive (FH+) alcoholics, alcoholics with an antisocial personality disorder (ASPD), alcoholics with an ADHD, and type 1 or type 2 alcoholics according to Cloninger's typology. Compared to the control subjects, there was a significant excess of the -141C Del allele in alcoholics with a paternal and grandpaternal history of alcoholism and in alcoholic subgroups with suicidality or without a history of withdrawal symptoms. There were no significant differences in allele frequency between the entire group or subgroups of alcoholics and healthy controls. Therefore, the -141C Del variant of the DRD2 might be a protective factor against the development of withdrawal symptoms. However, it might also be a risk factor in a highly burdened subgroup of alcoholics with a paternal and grandpaternal history of alcoholism and it might contribute to the substantially higher likelihood of suicide in alcoholics.

Hormonal changes with cholesterol reduction: a double-blind pilot study

BACKGROUND

The lowering of high serum cholesterol levels may be associated with increased non-cardiac mortality due to behavioral changes, although such endpoints are likely rare.

OBJECTIVE

This current study sought to determine if hormonal changes accompany pharmacologically induced decreases in serum cholesterol levels.

METHOD

Cholesterol, dopamine, homovanillic acid (HVA), serotonin, 5-HIAA, testosterone, cortisol and pregnenolone were measured at baseline and after 4 weeks of treatment.

RESULTS

Subjects' cholesterol levels significantly declined within 4 weeks. Concomitant significant increase in dopamine and HVA were noted.

CONCLUSION

Although this study is limited in size, it raises the possibility that cholesterol-lowering drug treatment is associated with hormonal perturbations.

Effects of antidepressant treatment on thyrotropin-releasing hormone stimulation, growth hormone response to L-DOPA, and dexamethasone suppression tests in major depressive patients

Dexamethasone suppression (DST), thyroid-stimulating hormone (TSH) and prolactin (PRL) responses to thyrotropin-releasing hormone (TRH) and growth hormone (GH) response to L-DOPA tests were evaluated in 19 depressed inpatients before the commencement of the antidepressant treatment and after the clinical response to examine: (i) the functional relationships among the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-thyroid (HPT) axis and dopaminergic system in depression, (ii) any alterations in these hormonal functions with the antidepressant treatment. TSH responses to TRH showed a tendency to increase from pre- to posttreatment period, while TRH-induced PRL and L-DOPA-induced GH responses did not change with treatment in depressed patients who responded to the treatment. Females showed significantly higher TSH and PRL responses to TRH compared to males. No interconnections were found among the responses in DST, TRH stimulation test and L-DOPA-induced GH test in the patients. The results do not support the interrelations between the abnormalities in the HPT and HPA axes and central dopaminergic activity in depression.

Catecholamine and HPA axis dysfunction in depression: relationship with suicidal behavior

A large body of evidence suggests a potential role for catecholaminergic function as a possible biological factor in the control of suicidal behavior. Recently, we have used a neuroendocrine strategy to study dopaminergic and noradrenergic activities in depressed suicide attempters. However, some problems are associated with the use of growth hormone (GH) response to catecholaminergic challenge, because GH release could be decreased by a direct effect of corticosteroids at the pituitary level. Therefore, the purpose of the present study was to assess GH response to both apomorphine, a dopaminergic agonist, and clonidine, an alpha2-adrenergic agonist, according to the dexamethasone suppression test (DST) status in a sample of 20 major depressed inpatients with a history of suicide attempt compared with nonattempters. Our results tended to show that hypercortisolemia as assessed by post-DST cortisol values did not inhibit GH response to apomorphine or clonidine, suggesting that hypothalamo-pituitary-adrenal axis overactivity does not explain the impaired GH response to apomorphine in major depressed patients with a history of suicide attempt.

Understanding the neurobiology of suicidal behavior

Our current knowledge about the neurobiology of suicide is still limited. Technical limitations and the complexity of the CNS are major obstacles. However, there is evidence for a hereditary disposition to suicide, which appears to be independent of diagnosis. Clinical, postmortem, genetic, and animal studies suggest that serotonin has a central role. The main regions of interest in the CNS have been the dorsal and median raphe nuclei in the midbrain that host the main serotonergic cell bodies and the prefrontal cortex, particularly the ventral PFC, innervated by the serotonergic system. In vivo and postmortem studies indicate serotonergic hypofunction in suicide and serious suicide attempts. This deficiency in turn can lead to a predisposition to impulsive and aggressive behavior, probably due to a breakdown in the inhibitory function of the ventral prefrontal cortex as a result of less serotonin input. In the context of this predisposition and the development of mental illness or other life stressors, the individual is at risk of acting on suicidal thoughts. Such deficient serotonin input into the PFC may arise as a result of genetic, parenting, head injury, and other effects. Identifying psychiatric, social, and environmental predictors of suicide are studied to improve prediction and prevention of suicide. A better understanding of the neurobiology of suicide can help detect at risk populations and help develop better treatment interventions.

Role of dopamine in non-depressed patients with a history of suicide attempts

Several data are available about the implication of the dopaminergic system in the control of inward-directed aggression. Previously, we suggested an involvement of D2-dopaminergic function in the expression of suicidal behavior by demonstrating a smaller growth hormone (GH) response to apomorphine, a dopaminergic agonist, in depressed patients with a history of suicide attempts in comparison to non-attempters. In the present study, in order to test this hypothesis, GH responses to intravenous apomorphine were measured in non-depressed patients with a history of suicide attempts. The study was performed in 17 non-depressed male patients with a score less than 12 on the 17-item HAMD. The patients were subgrouped into suicide attempters (N = 7) and non-attempters (N = 10). Mean GH peak responses to apomorphine differed significantly between suicide attempters and non-attempters: (mean +/- SD) for GH peak, 10.4 +/- 8.2 ng/mL vs 27.3 +/- 13.1 ng/ml, F = 9.0, P = 0.009. In conclusion, dopaminergic disturbances seem to play a role in the biology of inward-directed aggression in non-depressed patients.

Reduced dopamine function in depressed patients is related to suicidal behavior but not its lethality

Several lines of evidence suggest a role for dopamine in the control of suicidal behaviour. Previously, we suggested an involvement of D2-dopaminergic function in the biology of suicide by demonstrating a smaller growth hormone (GH) response to apomorphine, a dopaminergic agonist, in depressed patients who later died by suicide. The purpose of the present study was to assess GH response to apomorphine in major depressed in-patients with a history of highly lethal suicide attempt compared to depressed patients with a low lethal lifetime suicide attempt history and non-attempters. The study was performed in a sample of 26 male depressed in-patients with a history of suicide attempt compared to 26 male depressed non-attempters. We observed a significant difference between suicide attempters and non-attempters (for GH peak, 6.3+/-5.1 ng/ml vs 15.8+/-14.2 ng/ml, F=10.3, df=1, 50, P=0.002). Moreover, GH peak responses to apomorphine did not differ between depressed patients with a high lethal lifetime suicide attempt history and patients who made low lethal lifetime suicide attempt. In conclusion, the results of the present study support a role for dopamine in the biology of suicidal behaviour. More specifically, an impaired GH response to apomorphine could be a marker of suicide risk.

Reduced dopaminergic activity in depressed suicides

Several data are available about the implication of the dopaminergic system in the control of inward-directed aggression. Previously, we suggested an involvement of D2-dopaminergic function in the expression of suicidal behavior by demonstrating a smaller growth hormone (GH) response to apomorphine, a dopaminergic agonist, in depressed patients with a history of suicide attempts in comparison to nonattempters. In the present study, the purpose was to analyze GH responses to apomorphine in depressive patients who later died by suicide. Our sample comprised eight male depressive inpatients who died by suicide within one year after hospitalisation. These patients were compared to 18 male major depressed inpatients who never attempted suicide. Mean GH peak responses to apomorphine differed significantly between suicide completers and controls (mean +/- SD): for GH peak, 7.6 +/- 4.1 ng/ml vs 18.9 +/- 14.2 ng/ml, U = 30, Z = -2.33, P = 0.02. Our results tend to confirm the role of dopamine in the biology of suicide in depression.

The flinders sensitive line rats, a genetic model of depression, show abnormal serotonin receptor mRNA expression in the brain that is reversed by 17beta-estradiol

The possible link between estrogen and serotonin (5-HT) in depression was investigated using a genetic animal model of depression, the Flinders Sensitive Line (FSL) rats, in comparison to control Flinders Resistant Line rats. The mRNA levels of the estrogen receptor (ER) alpha and beta subtypes and the 5-HT(1A) and 5-HT(2A) receptors were analyzed in several limbic-related areas of ovariectomized FSL and FRL rats treated with 17beta-estradiol (0.15 microg/g) or vehicle. The FSL animals were shown to express significantly lower levels of the 5-HT(2A) receptor transcripts in the perirhinal cortex, piriform cortex, and medial anterodorsal amygdala and higher levels in the CA 2-3 region of the hippocampus. The only significant difference between the rat lines in ER mRNA expression was found in the medial posterodorsal amygdala, where the FSL rats showed lower ERalpha expression levels. Overall, estradiol treatment increased 5-HT(2A) and decreased 5-HT(1A) receptor mRNA levels in several of the examined regions of both lines. Thus, in many areas, estradiol was found to regulate the 5-HT receptor mRNA expression in the opposite direction to the alterations found in the FSL rats. These findings further support the implication of 5-HT receptors, in particular the 5-HT(2A) subtype, in the etiology of affective disorders. Moreover, the ability of estradiol to regulate the expression of the 5-HT(1A) and 5-HT(2A) receptor genes might account for the reported influence of gonadal hormones in mood and depression.

Neuropathology of suicide. A review and an approach

Neuropathology is one approach to the effort to elucidate the pathophysiology of suicide. Initial neurochemical studies focusing on the roles of serotonin (5-HT) and noradrenaline (NE) abnormalities in brains of suicide victims have been somewhat inconsistent. More recently developed methodologies, including quantitative receptor autoradiography, immunoblotting, immunohistochemistry, cell morphometry, in situ hybridization, Northern analysis, solution hybridization/RNase protection assay, reverse transcriptase polymerase chain reaction, and genotyping, which have already been applied successfully in studies of other disorders of brain structure or function, are now increasingly being adopted for postmortem studies of suicide. These new strategies are adding convergent evidence for brain 5-HT and NE dysfunction in the etiology of suicide susceptibility, refining the neuroanatomical localization of this dysfunction, and in addition, implicating heretofore unsuspected candidate neurotransmitter systems in the neuropathological substrates of suicide susceptibility. It is argued here that the confluence of the availability of suitable postmortem samples and this augmentation of our armamentarium of techniques promises the attainment of important new insights into the biological underpinnings of suicide from postmortem research. It is to be hoped that this new knowledge might inspire novel pharmacotherapeutic strategies for the prevention of suicide.

Reduced dopamine turnover in the basal ganglia of depressed suicides

We have measured the concentrations of dopamine, and the dopamine metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC), in five brain regions from suicide victims with a firm retrospective diagnosis of depression, and matched controls. The suicides were divided into those free of antidepressant drugs and those in whom prescription of antidepressant drugs was clearly documented. DOPAC concentrations were significantly lower in caudate, putamen and nucleus accumbens of antidepressant-free suicides compared to controls. In antidepressant-treated suicides, lower concentrations of DOPAC were observed in the basal ganglia, reaching statistical significance in caudate. Lower DOPAC concentrations were largely restricted to those suicides who died by non-violent methods. There were no significant differences in dopamine and HVA concentrations in either suicide group compared to controls, although there was a trend for HVA concentrations to be lower in suicides. This study provides evidence for reduced dopamine turnover, as judged from reduced DOPAC levels, in depressed suicides, although we cannot exclude the possibility that this may be due to ingestion of toxic agents.

Serotonergic, noradrenergic, and dopaminergic measures in suicide brains

Concentrations of the three main monoamines (5-HT, NA, and DA), their metabolites (5-HIAA, DOPAC, and HVA), and the serotonin precursor 5-hydroxy-L-tryptophan were simultaneously measured in frontal cortex, gyrus cinguli, and hypothalamus from 23 controls and 18 suicide victims. Overall suicides did not show significant differences with respect to the control group in any of the measured compounds. Significant increases in noradrenaline and dopamine concentrations were noted in the carbon monoxide poisoning suicides, together with a significant increased hypothalamic dopamine in the drug overdose suicides. It is suggested that the suicidal behavior is not related to substantial changes in cortical and hypothalamic monoaminergic function; however, the reported results could be secondary to the rapid effect of hypoxia and of the acute self-administration of certain drugs in specific metabolic pathways.

Brain monoaminergic and neuropeptidergic variations in human aging

The effect of age on the monoamines 5-hydroxytryptamine (5-HT), noradrenaline (NA) and dopamine (DA), their metabolites 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), 3,4-dihydroxphenylacetic acid (DOPAC), and the 5-HT precursor 5-hydroxy-L-tryptophan (5-HTP), together with the peptides neuropeptide Y (NPY), somatostatin (SOM), and corticotropin-releasing factor (CRF), was studied in frontal cortex, gyrus cinguli and hypothalamus from 23 healthy control subjects, aged 16-75 years. After correcting for postmortem interval, significant decreases in gyrus cinguli NA, NPY and CRF, and hypothalamic DA, HVA, and 5-HIAA concentrations were obtained with advancing age. The involvement of the monoaminergic system in several functional abnormalities appearing in senescence is suggested. Furthermore, evidence is given of the participation of the peptidergic systems in the aging process.

Effect of aging on lazabemide binding, monoamine oxidase activity and monoamine metabolites in human frontal cortex

Age-related modifications of monoamine oxidase-A and -B (MAO-A and MAO-B) and amine metabolite concentrations were studied in human frontal cortex taken postmortem from 22 subjects of various ages (21-75 years). Qualitative and quantitative analysis for MAO-B was provided by kinetic studies with a specific radioligand, [3H]lazabemide. The data demonstrated a significant (P < 0.05) positive correlation between the density of [3H]lazabemide binding sites (Bmax) and age of the subject, without showing an apparent modification in the dissociation constant (KD) of the radioligand. In parallel experiments, MAO-B but not MAO-A activity was shown to correlate with age (P < 0.05). The concentrations of the amine metabolites 4-hydroxy-3-methoxyphenylacetic acid (HVA), 5-hydroxyindole-3-acetic acid (5-HIAA), 3,4-dihydroxyphenylacetic acid (DOPAC), 4-hydroxy-3-methoxyphenylglycol (MHPG) and 3,4-dihydroxyphenylglycol (DHPG) were all devoid of a correlation with age. Neither did the concentrations of these metabolites relate to the respective subject's MAO-B enzymatic activity nor to [3H]lazabemide Bmax. A correlation, though rather weak, was obtained between MAO-A activity and MHPG concentration (P = 0.045). The MAO-A and -B enzyme characteristics in subjects who had committed suicide (n = 9) did not differ from those of subjects deceased for other causes (n = 13). Among the measured monoamine metabolites the concentrations of DOPAC and HVA were higher in the suicide versus control group (P < 0.05). The present data confirm in a direct manner that the increase in MAO-B activity in aging brain is due to an enhancement of the number of active sites of the enzyme and not through modifications of its kinetic characteristics. Furthermore, that neither the characteristics nor the activity of the enzyme are changed in the frontal cortex of suicide victims compared to control subjects.

3H-imipramine binding in the frontal cortex of suicides

Imipramine binding (desipramine- and serotonin-sensitive) was determined in the frontal cortex of suicide victims and nonpsychiatric controls who died due to medical disease or accidents. There were no differences in Kd or Bmax of imipramine binding between controls and suicides. The Kd and Bmax values of serotonin-sensitive imipramine binding were significantly lower than desipramine-sensitive imipramine binding, both in controls and suicides. There were significant correlations between Kd and Bmax of serotonin-sensitive imipramine binding and desipramine-sensitive imipramine binding in suicides but not in controls.