Reduced dopaminergic activity in depressed suicides

Between Temperament and Psychopathology: Examples from Neuropharmacological Challenge Tests in Healthy Humans

BACKGROUND

This paper tries to demonstrate that the questionnaire-based continuum between temperament traits and psychopathology can also be shown on the biochemical level. A common feature is the incapacity to adapt to external demands, as demonstrated by examples of disturbed hormone cycles as well as neurotransmitter (TM) responses related to affective and impulse control disorders.

METHODS

Pharmacological challenge tests performed in placebo-controlled balanced crossover experiments with consecutive challenges by serotonin (5-HT), noradrenaline (NA), and dopamine (DA) agonistic drugs were applied to healthy subjects, and individual responsivities of each TM system assessed by respective cortisol and prolactin responses were related to questionnaire-based facets of depressiveness and impulsivity, respectively.

RESULTS

The depression-related traits "Fatigue" and "Physical Anhedonia" were characterized by low and late responses to DA stimulation as opposed to "Social Anhedonia," which rather mirrored the pattern of schizophrenia. Reward-related and premature responding-related impulsivity represented by high scores on "Disinhibition" and "Motor Impulsivity," respectively, as well as the questionnaire-based components of attention deficit hyperactivity disorder, "Cognitive" and "Motor Impulsivity," could be discriminated by their patterns of DA/NA responses. 5-HT responses suggested that instead of the expected low availability of 5-HT claimed to be associated with impulse control disorders, low NA responses indicated lack of inhibition in impulsivity and high NA responses in depression-related "Anhedonia" indicated suppression of approach motivation.

CONCLUSIONS

In spite of the flaws of pharmacological challenge tests, they may be suitable for demonstrating similarities in TM affinities between psychopathological disturbances and respective temperament traits and for separating sub-entities of larger disease spectra.

Hippocampal monoamine changes in the Flinders sensitive line rat: A case for the possible use of selective α2C-AR-antagonists in stress and anxiety disorders in companion animals

Non-selective α₂-adrenoreceptor (AR) stimulation delivers favourable sedative, analgesic, muscle relaxant and anxiolytic actions in companion animals, but is associated with cardiovascular and respiratory side effects. Anxiety conditions underscore monoamine disturbances amenable to α₂-AR modulation. We investigated sub-chronic (14 day s.c.) treatment with the selective α_2C-AR antagonist, ORM-10921 (0.03, 0.1, 0.3 mg/kg/d) on hippocampal noradrenaline (NA), dopamine (DA), serotonin (5-HT) and their turnover levels in stress sensitive Flinders Sensitive Line (FSL) rats versus Flinders Resistant Line (FRL) controls, using high performance liquid chromatography. The effects of ORM-10921 were compared to the non-selective α₂-AR antagonist, idazoxan (IDAZ; 3 mg/kg/d), and to imipramine (IMI; 15 mg/kg/d), a reference antidepressant in this model. FSL rats displayed significantly reduced 5-HT (p = 0.03) and DA (p = 0.02) levels vs. FRL controls, while NA levels showed a similar trend. ORM-10921 significantly increased NA (all doses p ≤ 0.02), 5-HT (0.1 and 0.3 mg/kg p ≤ 0.03) and DA levels (all doses p ≤ 0.03), which correlated with decreased monoamine turnover. In contrast, IDAZ significantly elevated NA (p < 0.005) and DA (p < 0.004) but not 5-HT levels. IMI also significantly increased 5-HT (p < 0.009), with a tendency to increase NA (p = 0.09) but not DA. ORM-10921 exerts similar albeit broader effects on hippocampal monoamines than IDAZ, explaining earlier established efficacy associated with α_2C-AR antagonism in animal models of depression and cognitive dysfunction. These and the current studies encourage application of ORM-10921 in depression in humans, as well as raise the intriguing possibility that selective α_2C-AR antagonists may be beneficial in anxiety and stress-related disorders in companion animals. Both warrant further study.

Hopelessness, Dissociative Symptoms, and Suicide Risk in Major Depressive Disorder: Clinical and Biological Correlates

Background: Major depressive disorder (MDD) has different clinical presentations and is associated with neurobiological alterations. Hopelessness, anhedonia, and dissociation represent some of the most pervasive psychopathological symptoms that often lead to suicidal thoughts, attempts, and actions. To further research on the concept of depression endophenotypes, this study aimed to assess the possible relationships between hopelessness and other clinical and biological correlates (i.e., striatal dopaminergic dysfunction) in depressed patients. Methods: We recruited 51 subjects with MDD. All subjects underwent ¹²³I-FP-CIT SPECT to assess striatal dopamine transporter (DAT) availability and a psychometric evaluation using the psychometric scale to assess depressive, anxious, dissociative, and hopelessness symptoms aside from suicidal ideation. Result: An inverse correlation between the hopelessness score and dopamine transporter availability in all basal ganglia was bilaterally found. (Right Putamen, r = −0.445, p < 0.01; Left Putamen, r = −0.454, p < 0.01; Right Caudate, r = −0.398, p < 0.01; Left Caudate, r = −0.467, p < 0.01) Moreover, a positive correlation was also found between hopelessness and dissociative symptoms. Conclusions: These results provide important evidence on the neurobiological and clinical correlates of different psychopathological symptoms of depression with potential implications in terms of devising more effective treatment programs.

Aggressive behavior in psychiatric patients in relation to hormonal imbalance (Review)

Aggressive behavior is one of the main characteristics of different psychiatric disorders such as: personality disorders (antisocial personality disorder, borderline personality disorder), schizophrenia, intermittent explosive disorder, post-traumatic stress disorder, bipolar disorder, depression, alcohol/substance induced psychiatric disorders. Epidemiological evidence shows that always there is a higher risk of violence and aggressivity among patients with psychiatric disorders compared with general population. Researchers have tried many times to narrow the theories that can explain such a behavior, starting from models that involve a link between illness and aggression going up to external-environmental factors including the therapeutic relation in the hospital. Even if the majority of studies are centered on intoxications (with alcohol or other substances that potentiate the aggressive behavior) we will highlight another somatic dimension linked with this behavior. In the following review we summarize the hormonal imbalances that have been noted to accompany aggressive behavior in different psychiatric disorders. Several studies have been made starting even at the age of ten corelating hormone cortisol with increase aggression, but patients with psychiatric disorders have a higher sensitivity in linking hormonal imbalance with their behavior.

Benefits and limitations of drug studies in temperament research: biochemical responses as indicators of temperament

This paper presents a discussion of principles and problems of neurotransmitter challenge tests using examples of experiments, most of which were performed in the author's laboratory. Drugs targeting synthesis, release, receptors or reuptake of dopamine, serotonin and noradrenergic transmitter (TM) systems were used for characterizing or discriminating certain temperament or personality traits and their sub-factors. Any personality or temperament trait is characterized by multiple TM responses, thus constellations of hormone responses to drugs acting on different TM systems or on different sources of TM activity were investigated within individuals in crossover designs. The major conclusions are: (i) intra-individual patterns of hormone responses to different TM-related drugs, or to agonists and antagonists, can help to discriminate subtypes of temperament dimensions, and (ii) the latency and shape of response curves may help specify processes of biological responses related to psychological dimensions and reveal common TM sensitivities in clusters of traits. TM sensitivity, defined by hormone responses, does not always correspond to accompanying behavioural indicators, but may provide more specific information on underlying mechanisms. Additional consideration of drug doses and experimental induction of stressors may serve to identify temperament-related susceptibilities to certain drugs. Limitations of the challenge approach and recommendations for future research are discussed.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

Research on potential biomarker correlates for suicidal behavior: A review

Suicide is a world health priority. Studies over the last few decades have revealed the complexity underlying the neurobiological mechanisms of suicide. Researchers have found dysregulations in the serotonergic system, the stress system, neural plasticity, lipid metabolism, and cell signaling pathways in relation to suicidal behaviors. These findings have provided more insight into the final path leading to suicide, at which medical intervention should be applied to prevent the action. However, because these molecular mechanisms have been implicated in both depression and suicide, the specificity of the mechanisms has been obscured. In this review, we summarize the main findings of studies on molecular mechanisms of suicidal behavior from the last 2 decades, with particular emphasis on the potential, independent role of each mechanism that is not contingent upon an underlying psychopathology, such as depression. The act of suicide is multifactorial; no single molecular mechanism is sufficient to fully account for the act. Knowledge of the reciprocal interactions among these molecular mechanisms and studying them in the context of brain circuitry by using neuroimaging techniques will provide a better understanding of the neurobiology of suicide.

Dysregulation of Striatal Dopamine Receptor Binding in Suicide

Inconsistent evidence implicates disruptions of striatal dopaminergic indices in suicide and major depression. To determine whether there are alterations in the striatal dopamine system in suicide, we conducted a quantitative autoradiographic survey of dopamine transporter (DAT; [³H]mazindol), D1 receptor ([³H]SCH23390), and D2 receptor ([³H]sulpiride) binding in the dorsal striatum postmortem from matched suicides and controls. Axis I and axis II psychiatric diagnosis, recent treatment history, and early life adversity (ELA) were determined by psychological autopsy. Mean DAT, D2, and D1 receptor binding did not differ in suicide. However, there was a positive correlation between D1 and D2 receptor binding in the dorsal striatum of control subjects (R²=0.31, p<0.05) that was not present in suicides (R²=0.00, p=0.97). In suicides and controls with reported ELA, there was no correlation between striatal DAT and D1 receptor binding (R²=0.07, p=0.33), although DAT and D1 receptor binding was positively correlated in subjects with no report of ELA (R²=0.32, p<0.05). After controlling for age, there were no significant ELA-related mean differences. Binding of D1 receptors and DAT throughout the striatum correlated negatively with age (D1 receptor: R²=0.12, p<0.05; DAT: R²=0.36, p<0.001). There appears to be an imbalance in dopaminergic receptor and transporter expression related to suicide that differs from that associated with ELA or age.

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.

Catechol-O-methyltransferase Val158Met polymorphism and altered COMT gene expression in the prefrontal cortex of suicide brains

Catechol-O-methyltransferase (COMT) plays a key role in the degradation of catecholamine neurotransmitters within the brain. A functional polymorphism COMT Val158Met has been associated with psychiatric disorders including suicidal behavior. In the present study we examined whether this polymorphism was related to COMT mRNA expression in frontal cortical regions, and whether the expression of COMT differed between depressed suicide victims and psychiatric healthy controls. The Val158Met polymorphism was determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis. The levels of COMT mRNA expression in the frontopolar cortex (FPC; 29 suicides vs. 27 controls) and orbital frontal cortex (OFC; 19 suicides vs. 15 controls) were significantly increased among depressed individuals that died by suicide relative to those of controls, being up-regulated by approximately 60% and 65% in the FPC and OFC, respectively. Furthermore, among individuals with the Met allele (Met/Met and Met/Val genotypes) who died by suicide COMT mRNA expression was elevated relative to that of the nondepressed Met allele carriers. However, significant differences were not detected between suicides (n=49) and controls (n=72) with respect to the Val158Met genotypic distribution and allelic frequencies. These results are consistent with the perspective that altered COMT mRNA expression in frontal cortical brain regions might contribute to suicide and/or depression, further supporting the role of dysregulation of catecholaminergic pathway genes in the pathophysiology of suicide behaviors.

Mapping anhedonia onto reinforcement learning: a behavioural meta-analysis

Background

Depression is characterised partly by blunted reactions to reward. However, tasks probing this deficiency have not distinguished insensitivity to reward from insensitivity to the prediction errors for reward that determine learning and are putatively reported by the phasic activity of dopamine neurons. We attempted to disentangle these factors with respect to anhedonia in the context of stress, Major Depressive Disorder (MDD), Bipolar Disorder (BPD) and a dopaminergic challenge.

Methods

Six behavioural datasets involving 392 experimental sessions were subjected to a model-based, Bayesian meta-analysis. Participants across all six studies performed a probabilistic reward task that used an asymmetric reinforcement schedule to assess reward learning. Healthy controls were tested under baseline conditions, stress or after receiving the dopamine D₂ agonist pramipexole. In addition, participants with current or past MDD or BPD were evaluated. Reinforcement learning models isolated the contributions of variation in reward sensitivity and learning rate.

Results

MDD and anhedonia reduced reward sensitivity more than they affected the learning rate, while a low dose of the dopamine D₂ agonist pramipexole showed the opposite pattern. Stress led to a pattern consistent with a mixed effect on reward sensitivity and learning rate.

Conclusion

Reward-related learning reflected at least two partially separable contributions. The first related to phasic prediction error signalling, and was preferentially modulated by a low dose of the dopamine agonist pramipexole. The second related directly to reward sensitivity, and was preferentially reduced in MDD and anhedonia. Stress altered both components. Collectively, these findings highlight the contribution of model-based reinforcement learning meta-analysis for dissecting anhedonic behavior.

Multifinality in the development of personality disorders: a Biology x Sex x Environment interaction model of antisocial and borderline traits

Although antisocial personality disorder (ASPD) is more common among males and borderline PD (BPD) is more common among females, some authors have suggested that the two disorders reflect multifinal outcomes of a single etiology. This assertion is based on several overlapping symptoms and features, including trait impulsivity, emotional lability, high rates of depression and suicide, and a high likelihood of childhood abuse and/or neglect. Furthermore, rates of ASPD are elevated in the first degree relatives of those with BPD, and concurrent comorbidity rates for the two disorders are high. In this article, we present a common model of antisocial and borderline personality development. We begin by reviewing issues and problems with diagnosing and studying PDs in children and adolescents. Next, we discuss dopaminergic and serotonergic mechanisms of trait impulsivity as predisposing vulnerabilities to ASPD and BPD. Finally, we extend shared risk models for ASPD and BPD by specifying genetic loci that may confer differential vulnerability to impulsive aggression and mood dysregulation among males and impulsive self-injury and mood dysregulation among females. Although the precise mechanisms of these sex-moderated genetic vulnerabilities remain poorly understood, they appear to interact with environmental risk factors including adverse rearing environments to potentiate the development of ASPD and BPD.

Dopa decarboxylase and tyrosine hydroxylase gene variants in suicidal behavior

The dopaminergic system has been previously associated to behavioral facilitation and aggression, hence making the pathway a good candidate for suicidal behavior. We studied gene variants in the tyrosine hydroxylase (rs3842727, rs6356) and DOPA decarboxylase (rs1451371, rs1470750, rs998850) genes in a sample of 571 individuals consisting of 167 German suicide attempters (affective spectrum n = 107, schizophrenia spectrum n = 35, borderline personality disorder n = 25), 92 Caucasian individuals who committed suicide and 312 German control subjects. TH variants were not associated with suicide (uncorrected P = 0.023) and related traits. Some marginal associations could be observed for DDC with suicide, violence, anger, and aggression. In conclusion, our study does not support the involvement of TH gene variants as major contributors to suicide, whereas DDC variants could mediate some features related to suicide and be involved in violent suicidal behavior.

Increased incidence of pituitary microadenomas in suicide victims

BACKGROUND

Current data suggest an influence of the hypothalamic-pituitary-adrenal axis on suicidal behavior. The frequency of pituitary adenomas in suicide victims has not yet been investigated.

OBJECTIVES

The aim of this study was to assess whether the incidence of pituitary adenomas is correlated with suicide.

METHODS

Serial sections of 151 human pituitary glands obtained upon autopsy were examined microscopically. The glands were collected from 70 suicide victims and 81 subjects whose deaths were classified as unexpected or accidental (nonsuicidal group). The sections were stained with hematoxylin-eosin and the presence of adenoma was confirmed by immunostaining for collagen III.

RESULTS

In the suicidal group, pituitary microadenomas were found in 32 cases (47.7%), while in the nonsuicidal group microadenomas were detected in 15 cases (18.3%). The observed difference was statistically significant (p = 0.0003). The relative risk ratio of suicide in persons with pituitary adenomas was estimated at 1.9. Logistic regression analysis in a model controlled for age and sex showed that microadenomas constituted a unique risk factor in this model. The immunohistochemical phenotyping revealed a higher percentage of immunopositive (secreting) microadenomas in the nonsuicidal group as compared to the suicidal group (80.0 vs. 59.38%) and a predominance of growth hormone-secreting microadenomas in both groups. However, these differences as well as differences in the hormonal profiles of microadenomas between the groups were not significant.

CONCLUSIONS

These results suggest that pituitary adenomas belong to suicide risk factors.

Low plasma BDNF is associated with suicidal behavior in major depression

Brain-derived neurotrophic factor (BDNF), the most abundant neurotrophin in the brain, has a known association with the pathophysiology of anxiety and depression. However, the role of BDNF in suicide has not been well investigated to date. This study examined plasma BDNF levels in 32 major depressive disorder (MDD) patients who had recently attempted suicide, 32 non-suicidal MDD patients, and 30 normal controls. The lethality of the suicide attempt was measured using the Risk-Rescue Rating (RRR) and Lethality Suicide Attempt Rating Scale (LSARS). The severity of depression was measured with the Hamilton Depression Rating Scale (HDRS). Plasma BDNF levels were measured by enzyme linked immunosorbent assay. BDNF levels were significantly lower in suicidal MDD patients (430.5+/-397.0 pg/ml) than non-suicidal MDD patients (875.80+/-663.02 pg/ml) or normal controls (889.4+/-611.3 pg/ml) (F=6.682, p=0.002). The most suitable cut-off point of BDNF level between suicidal depression and non-suicidal depression groups was 444.58 pg/ml. At this cut-off point, the sensitivity=68.7%, specificity=78.1%, positive predictive value=75.9%, and negative predictive value=71.4%. However, there was no significant difference in BDNF levels between the depressive control and normal control groups (p=0.996). LSARS and RRR did not reveal any significant correlations with BDNF levels in suicidal patients. In addition, BDNF levels were not different between fatal and non-fatal suicide attempts. These results suggest that reduction of plasma BDNF level is related to suicidal behavior in major depression and that BDNF level may be a biological marker of suicidal depression.

Regional brain serotonin and dopamine transporter binding capacity in suicide attempters relate to impulsiveness and mental energy

To study different aspects of regional pre-synaptic brain (123)I-beta-CIT uptake on serotonin and dopamine re-uptake sites in drug-free suicide attempters in comparison with age- and sex matched control subjects, single photon emission computed tomography (SPECT) measurements were analysed for regional serotonin re-uptake (5HTT) and dopamine re-uptake (DAT) capacity (binding potential, BP()) after i.v. (123)I-beta-CIT administration. All suicide attempters were examined concerning seriousness of the attempt, and DSM-IV diagnosis. Both suicide attempters and control subjects were tested for psychotropic drugs, and completed the Marke-Nyman Temperament (MNT) test, including solidity (level of impulsiveness/initiative) and validity (level of mental energy). We found no significant difference between suicide attempters and control subjects concerning the regional levels of 5HTT BP() or DAT BP(). However, in suicide attempters, but not controls, we found significant regional correlations between MNT variables and SPECT results. We interpret the discrepant findings in suicide attempters and control subjects to be due to a disability of the suicide attempters to regulate their serotonin and dopamine levels, e.g. in response to external stress.

Prolactin Levels in Workers Exposed to Chemical, Physical and Psycho‐Social Urban Stressors

The aim of this study was to evaluate whether traffic police officers exposed to chemical, physical and psycho-social stressors, are at risk for alterations in plasma levels of prolactin (PRL) compared to a control group. Plasma PRL levels were evaluated in 92 male and 51 female, non-smoker, traffic police officers exposed to urban stressors and in 92 male and 51 female controls, matched by sex, age and working life (mean, SD and distribution), after excluding workers with the principal extra-occupational confounding factors. Mean PRL levels were significantly higher than controls in non-smoker, male and female traffic police officers (respectively, p=0.000 and p=0.013). The number of non-smoker, male and female traffic police officers with PRL values outside the upper normal limit for our laboratory was higher than, but not significantly different from controls. Mean PRL levels were not significantly higher than controls in smoker, male and female traffic police officers. The number of smoker, male and female traffic police officers with PRL values outside the normal limit for our laboratory was not significantly different from controls. The results suggest that exposure to urban chemical and physical stressors, interacting with psychosocial factors, may have an influence on PRL levels in traffic police officers. The level of plasma PRL might be a useful early biological marker for workers exposed to urban stressors.

Plasma levels of homovanillic acid, 5-hydroxyindoleacetic acid and cortisol, and serotonin turnover in depressed patients

Plasma levels of ACTH, cortisol and monoamines were examined in 23 depressed patients and 31 healthy subjects. Patients showed increased plasma cortisol levels, but not plasma adrenocorticotropic hormone (ACTH) levels. The plasma levels of a dopamine metabolite, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC), were significantly decreased in the patients. In contrast, the plasma levels of a serotonin (5-HT) metabolite, hydroxyindoleacetic acid (5-HIAA), and 5-HT turnover (5-HIAA/5-HT) were increased in the depressed patients. Therefore, plasma levels of HVA and 5-HIAA are proven to be dissociable. Furthermore, plasma levels of 5-HIAA and L-DOPA have positive relationships with severity of depression. On the basis of this and the previous studies, we speculate that an increase in the plasma 5-HIAA levels might be a compensatory mechanism for stress, whereas 5-HT turnover might reflect depressive state. Taken together, plasma levels of HVA and 5-HIAA, and 5-HT turnover (5-HIAA/5-HT) could be good markers for evaluating depression.

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.