Role of Serotonin and Dopamine System Interactions in the Neurobiology of Impulsive Aggression and its Comorbidity with other Clinical Disorders

Monoamine-sensitive developmental periods impacting adult emotional and cognitive behaviors

Development passes through sensitive periods, during which plasticity allows for genetic and environmental factors to exert indelible influence on the maturation of the organism. In the context of central nervous system development, such sensitive periods shape the formation of neurocircuits that mediate, regulate, and control behavior. This general mechanism allows for development to be guided by both the genetic blueprint as well as the environmental context. While allowing for adaptation, such sensitive periods are also vulnerability windows during which external and internal factors can confer risk to disorders by derailing otherwise resilient developmental programs. Here we review developmental periods that are sensitive to monoamine signaling and impact adult behaviors of relevance to psychiatry. Specifically, we review (1) a serotonin-sensitive period that impacts sensory system development, (2) a serotonin-sensitive period that impacts cognition, anxiety- and depression-related behaviors, and (3) a dopamine- and serotonin-sensitive period affecting aggression, impulsivity and behavioral response to psychostimulants. We discuss preclinical data to provide mechanistic insight, as well as epidemiological and clinical data to point out translational relevance. The field of translational developmental neuroscience has progressed exponentially providing solid conceptual advances and unprecedented mechanistic insight. With such knowledge at hand and important methodological innovation ongoing, the field is poised for breakthroughs elucidating the developmental origins of neuropsychiatric disorders, and thus understanding pathophysiology. Such knowledge of sensitive periods that determine the developmental trajectory of complex behaviors is a necessary step towards improving prevention and treatment approaches for neuropsychiatric disorders.

Val158Met COMT polymorphism and risk of aggression in alcohol dependence

Aggression, violence and antisocial behavior are common in alcoholism, but their biological basis is poorly understood. Several studies and recent meta-analyses indicate that in schizophrenia the catecholamine-O-methyltransferase (COMT) Val158Met genotype may be associated with aggression, most often in methionine allele carriers. We tested this hypothesis in a sample of treatment-seeking alcohol-dependent in-patients (293 German patients and 499 controls, and additional 190 Polish patients as replication sample). As expected, patients with a history of violent or non-violent crime were more often male, had an earlier onset of alcoholism and more withdrawal seizures and delirium tremens, and were more likely to have a history of suicide attempts. COMT genotype was not associated with a history of violent or non-violent crime. More studies are needed on the neurobiological basis of aggression and violence in alcoholism.

Self-injury in autism spectrum disorder: an effect of serotonin transporter gene promoter variants

Self-injurious behavior in autism spectrum disorder (ASD) has been associated with lower whole blood serotonin levels and the role of serotonin transporter gene promoter region (5HTTLPR) polymorphisms is of interest because of their effects on transporter functioning. This study examined the association between self-injurious behavior in ASD and allelic frequencies of 5HTTLPR. Sixty-four children and adolescents with ASD who were not taking serotonergic medication at the time of the assessment were included in the analysis. Self-injury was assessed using the Autism Diagnostic Interview-Revised (ADI-R) and whole blood serotonin levels were measured using high-pressure liquid chromatography (HPLC) with fluorometic detection. DNA was extracted from saliva and PCR amplified with fluorescent primers. Self-injury significantly increased with the number of La alleles of the 5HTTLPR and decreased with the number of Lg alleles. Self-injury in ASD may be associated with a specific genotype of the serotonin transporter gene promoter region. Future studies should continue to explore subgroups to clarify the underlying clinical and genetic heterogeneity in ASD.

No association between a polymorphism in the serotonin receptor 2B (HTR2B) gene and personality traits in healthy Japanese subjects

AIM

The brain neurotransmitter serotonin affects many aspects of human behavior, including personality traits. Because the serotonin receptor 2B (HTR2B) gene has recently been associated with impulsivity, we investigated the potential association between the rs10194776 and Q20* polymorphism in the HTR2B gene and personality traits in healthy subjects.

METHODS

A total of 1,171 healthy Japanese subjects were enrolled in this study. Their personality traits were evaluated using the Temperament and Character Inventory (TCI), and the rs10194776 and Q20* genotype was determined using real-time polymerase chain reaction.

RESULTS

There was a significant main effect of the rs10194776 polymorphism on harm avoidance and self-directedness in females (p = 0.037 and p = 0.043, respectively). However, these differences were insignificant after a Bonferroni correction. Subjects carrying the minor allele of the Q20* polymorphism were nonexistent.

CONCLUSION

The results of the present study suggest that the HTR2B polymorphism is not likely to be associated with personality traits, including novelty seeking and impulsivity.

Dopamine and serotonin signaling during two sensitive developmental periods differentially impact adult aggressive and affective behaviors in mice

Pharmacologic blockade of monoamine oxidase A (MAOA) or serotonin transporter (5-HTT) has antidepressant and anxiolytic efficacy in adulthood. Yet, genetically conferred MAOA or 5-HTT hypoactivity is associated with altered aggression and increased anxiety/depression. Here we test the hypothesis that increased monoamine signaling during development causes these paradoxical aggressive and affective phenotypes. We find that pharmacologic MAOA blockade during early postnatal development (P2-P21) but not during peri-adolescence (P22-41) increases anxiety- and depression-like behavior in adult (>P90) mice, mimicking the effect of P2-21 5-HTT inhibition. Moreover, MAOA blockade during peri-adolescence, but not P2-21 or P182-201, increases adult aggressive behavior, and 5-HTT blockade from P22-P41 reduced adult aggression. Blockade of the dopamine transporter, but not the norepinephrine transporter, during P22-41 also increases adult aggressive behavior. Thus, P2-21 is a sensitive period during which 5-HT modulates adult anxiety/depression-like behavior, and P22-41 is a sensitive period during which DA and 5-HT bi-directionally modulate adult aggression. Permanently altered DAergic function as a consequence of increased P22-P41 monoamine signaling might underlie altered aggression. In support of this hypothesis, we find altered aggression correlating positively with locomotor response to amphetamine challenge in adulthood. Proving that altered DA function and aggression are causally linked, we demonstrate that optogenetic activation of VTA DAergic neurons increases aggression. It therefore appears that genetic and pharmacologic factors impacting dopamine and serotonin signaling during sensitive developmental periods can modulate adult monoaminergic function and thereby alter risk for aggressive and emotional dysfunction.

Chronic Effect of Aspartame on Ionic Homeostasis and Monoamine Neurotransmitters in the Rat Brain

Aspartame is one of the most widely used artificial sweeteners globally. Data concerning acute neurotoxicity of aspartame is controversial, and knowledge on its chronic effect is limited. In the current study, we investigated the chronic effects of aspartame on ionic homeostasis and regional monoamine neurotransmitter concentrations in the brain. Our results showed that aspartame at high dose caused a disturbance in ionic homeostasis and induced apoptosis in the brain. We also investigated the effects of aspartame on brain regional monoamine synthesis, and the results revealed that there was a significant decrease of dopamine in corpus striatum and cerebral cortex and of serotonin in corpus striatum. Moreover, aspartame treatment significantly alters the tyrosine hydroxylase activity and amino acids levels in the brain. Our data suggest that chronic use of aspartame may affect electrolyte homeostasis and monoamine neurotransmitter synthesis dose dependently, and this might have a possible effect on cognitive functions.

Validation of a causal model of agitation among institutionalized residents with dementia in Taiwan

The aim of this study was to test a causal model of the predictors of agitation among 405 nursing home residents in Taiwan with varying degrees of cognitive impairment. Chart review and behavioral observations were used to assess residents' physical and psychosocial condition. The final version of the model had a good fit. Cognitive function and depression had direct effects on agitation, and pain and functional ability had indirect effects on agitation via depression. Additionally, cognitive function and pain influenced functional ability directly, which in turn influenced depression and ultimately influenced agitation. The results suggest that effective management of agitation in demented residents requires identifying the needs underlying the behavior rather than directly treating the behavior itself.

Cumulative adversity sensitizes neural response to acute stress: association with health symptoms

Cumulative adversity (CA) increases stress sensitivity and risk of adverse health outcomes. However, neural mechanisms underlying these associations in humans remain unclear. To understand neural responses underlying the link between CA and adverse health symptoms, the current study assessed brain activity during stress and neutral-relaxing states in 75 demographically matched, healthy individuals with high, mid, and low CA (25 in each group), and their health symptoms using the Cornell Medical Index. CA was significantly associated with greater adverse health symptoms (P=0.01) in all participants. Functional magnetic resonance imaging results indicated significant associations between CA scores and increased stress-induced activity in the lateral prefrontal cortex, insula, striatum, right amygdala, hippocampus, and temporal regions in all 75 participants (p<0.05, whole-brain corrected). In addition to these regions, the high vs low CA group comparison revealed decreased stress-induced activity in the medial orbitofrontal cortex (OFC) in the high CA group (p<0.01, whole-brain corrected). Specifically, hypoactive medial OFC and hyperactive right hippocampus responses to stress were each significantly associated with greater adverse health symptoms (p<0.01). Furthermore, an inverse correlation was found between activity in the medial OFC and right hippocampus (p=0.01). These results indicate that high CA sensitizes limbic-striatal responses to acute stress and also identifies an important role for stress-related medial OFC and hippocampus responses in the effects of CA on increasing vulnerability to adverse health consequences.

The neuromodulator of exploration: A unifying theory of the role of dopamine in personality

The neuromodulator dopamine is centrally involved in reward, approach behavior, exploration, and various aspects of cognition. Variations in dopaminergic function appear to be associated with variations in personality, but exactly which traits are influenced by dopamine remains an open question. This paper proposes a theory of the role of dopamine in personality that organizes and explains the diversity of findings, utilizing the division of the dopaminergic system into value coding and salience coding neurons (Bromberg-Martin et al., 2010). The value coding system is proposed to be related primarily to Extraversion and the salience coding system to Openness/Intellect. Global levels of dopamine influence the higher order personality factor, Plasticity, which comprises the shared variance of Extraversion and Openness/Intellect. All other traits related to dopamine are linked to Plasticity or its subtraits. The general function of dopamine is to promote exploration, by facilitating engagement with cues of specific reward (value) and cues of the reward value of information (salience). This theory constitutes an extension of the entropy model of uncertainty (EMU; Hirsh et al., 2012), enabling EMU to account for the fact that uncertainty is an innate incentive reward as well as an innate threat. The theory accounts for the association of dopamine with traits ranging from sensation and novelty seeking, to impulsivity and aggression, to achievement striving, creativity, and cognitive abilities, to the overinclusive thinking characteristic of schizotypy.

A new structure of a serotonin salt: comparison and conformational analysis of all known serotonin complexes

Four serotonin salt structures (serotonin adipate, C10H13N2O(+)·C6H9O4(-), is a previously unknown structure) were analysed to understand the influence of the anion on serotonin conformation. Hydrogen bonding alone favours a flat conformation, whereas additional stacking interactions between ions may possibly account for the nonplanar conformation. Since molecular conformation, stability and biological activity are interrelated, one can consider influencing the chemical and biological properties of serotonin by selecting an appropriate counter-ion for salt formation.

Neurotransmitter systems and neurotrophic factors in autism: association study of 37 genes suggests involvement of DDC

OBJECTIVES

Neurotransmitter systems and neurotrophic factors can be considered strong candidates for autism spectrum disorder (ASD). The serotoninergic and dopaminergic systems are involved in neurotransmission, brain maturation and cortical organization, while neurotrophic factors (NTFs) participate in neurodevelopment, neuronal survival and synapses formation. We aimed to test the contribution of these candidate pathways to autism through a case-control association study of genes selected both for their role in central nervous system functions and for pathophysiological evidences.

METHODS

The study sample consisted of 326 unrelated autistic patients and 350 gender-matched controls from Spain. We genotyped 369 tagSNPs to perform a case-control association study of 37 candidate genes.

RESULTS

A significant association was obtained between the DDC gene and autism in the single-marker analysis (rs6592961, P = 0.00047). Haplotype-based analysis pinpointed a four-marker combination in this gene associated with the disorder (rs2329340C-rs2044859T-rs6592961A-rs11761683T, P = 4.988e-05). No significant results were obtained for the remaining genes after applying multiple testing corrections. However, the rs167771 marker in DRD3, associated with ASD in a previous study, displayed a nominal association in our analysis (P = 0.023).

CONCLUSIONS

Our data suggest that common allelic variants in the DDC gene may be involved in autism susceptibility.

Role of Hypothalamic-pituitary-adrenal-axis in Affective Disorders: Anti-depressant and Anxiolytic Activity of Partial 5-HT1A Agonist in Adrenalectomised Rats

BACKGROUND

Depression is a neurological disorder characterized by sad mood, loss of pleasure, agitation and retardation. Though most relevant neuronal pathophysiology is characterized by decrease in monoamine namely; serotonin (5-HT), dopamine, noradrenaline level in central areas regulating mood and behavior, it inadequately explains the exact mechanism involved. Buspirone (BUS), a partial 5-HT1A receptor agonist has shown promising anti-depressant and anxiolytic properties in various pre-clinical and clinical studies, but the molecular and cellular mechanisms are still unclear.

OBJECTIVE

The aim of this study was to investigate, in vivo, the role of hypothalamic-pituitary-adrenal (HPA) axis dysregulation in pathophysiology of depression-related disorders and the anti-depressant like activity of BUS. To simulate HPA axis dysregulation, rats were subjected to bilateral adrenalectomy (ADX).

MATERIALS AND METHODS

We have analyzed effect of BUS (10 mg/kg, i.p.) in ADX and sham rats using open field, sucrose consumption, elevated plus maze and hyper-emotionality tests.

RESULTS

In all animal models tested, ADX rats exhibited significant depressive and anxiogenic states while BUS was effective in reversing the psychological diseased condition developed.

CONCLUSION

Taken together, these data showed a prominent role of HPA axis in depression and neuronal mechanism of BUS as anti-depressant and anxiolytic agent. Moreover, our findings suggest that BUS can be a better candidate for stress related depression and anxiety.

Disrupted ventromedial prefrontal function, alcohol craving, and subsequent relapse risk

IMPORTANCE

Alcohol dependence is a chronic relapsing illness; stress, alcohol-related cues, and neutral-relaxing states significantly influence craving and relapse risk. However, neural mechanisms underlying the association between these states and alcohol craving and relapse risk remain unclear.

OBJECTIVES

To identify neural correlates associated with alcohol craving and relapse outcomes in 45 treatment-engaged, 4- to 8-week abstinent alcohol-dependent (AD) patients, and to compare brain responses of 30 demographically matched AD patients and 30 healthy control subjects during stress, alcohol, and neutral-relaxing cues.

DESIGN

Functional magnetic resonance imaging study while participants were engaging in brief individualized script-driven imagery trials of stress, alcohol cues, and neutral-relaxing scenarios, and a prospective clinical outcome design to assess alcohol relapse 90 days postdischarge from inpatient treatment in the AD group.

SETTINGS

Inpatient treatment setting in a community mental health center and hospital-based research unit.

PATIENTS

Forty-five recovering AD patients in inpatient treatment for examining relapse, and 30 healthy control subjects demographically matched to 30 AD patients (subgroup of the relapse sample) for group comparisons.

INTERVENTION

Twelve-step recovery-based addiction treatment for the patient group.

MAIN OUTCOMES AND MEASURES

Brain response, alcohol craving, and relapse outcome measures (time to relapse and relapse severity).

RESULTS

Increased ventromedial prefrontal cortex (vmPFC) and anterior cingulate cortex (ACC) activation during neutral-relaxing trials was correlated with high alcohol cue-induced and stress-induced craving in early recovering AD patients (x = 6, y = 43, z = -6; P < .01, whole-brain corrected). This vmPFC/ACC hyperactivity significantly predicted subsequent alcohol relapse, with a hazards ratio greater than 8 for increased relapse risk. Additionally, vmPFC/ACC hyperactivation during neutral trials and reduced activity during stress trials were each predictive of greater days of alcohol used after relapse (P < .01, whole-brain corrected). In contrast, matched control subjects showed the reverse pattern of vmPFC/ACC responses to stress, alcohol cues, and relaxed trials (F = 6.42; P < .01, whole-brain corrected).

CONCLUSIONS AND RELEVANCE

Findings indicate that disrupted vmPFC/ACC function plays a role in jeopardizing recovery from alcoholism and may serve as a neural marker to identify those at risk for alcohol relapse.

Epilepsy and brain injury: a case report of a dramatic neuropsychiatric vicious circle

PRIMARY OBJECTIVE

Early treatment of epilepsy is warranted to avoid possible severe consequences. This study aimed to assess the value of treatment in a patient who developed epilepsy after major brain surgery.

DESIGN

Case description. A 51 years-old man had a history of putative petit mal seizures since adolescence and left frontotemporal lobectomy after a major traffic accident at age 17. He subsequently developed quickly generalizing partial complex seizures, associated with severe behavioural alterations and personality changes; the condition was left untreated. A further seizure-related loss of consciousness led to another traffic accident at age 47.

METHODS AND PROCEDURES

The patient was administered 200 mg/day topiramate, 600 mg/day quetiapine, 1000 mg/day valproate, 1200 mg/day gabapentin and 800 mg/day carbamazepine.

MAIN OUTCOMES AND RESULTS

The instituted anti-epileptic treatment reduced seizure frequency and severity, but did not affect psychiatric symptomatology, which even worsened. An association between anti-epileptic drugs with mood stabilizing properties and an atypical anti-psychotic dramatically improved psychiatric symptoms, but did not prevent the patient from needing long-term healthcare.

CONCLUSIONS

Long-term untreated epilepsy may expose to accident proneness and further psychiatric deterioration. Early diagnosis and treatment of epilepsy may help in avoiding a potentially lethal vicious circle.

The mediator roles of trait anxiety, hostility, and impulsivity in the association between childhood trauma and dissociation in male substance-dependent inpatients

The aim of this study was to investigate the mediator roles of negative affect, aggression, and impulsivity in the association between childhood trauma and dissociation in male substance-dependent inpatients. In addition, the effect of some variables that may be related with childhood trauma and dissociation among treatment-seeking substance dependents, such as substance of choice (alcohol/drug), mean of current age, and age at regular substance use was controlled. Participants were consecutively admitted 200 male substance-dependent inpatients. Patients were investigated with the Dissociative Experiences Scale, the Childhood Trauma Questionnaire, the Barratt Impulsiveness Scale, the Buss-Perry Aggression Questionnaire, the Beck Depression Inventory, and the Spielberger State-Trait Anxiety Inventory. Seventy-seven patients (38.5%) with pathologic dissociation were compared with 123 nondissociative patients (61.5%) classified by dissociative taxon membership. The dissociative group had lower age, age at regular substance use, duration of education, and higher rate of drug dependency rather than alcohol dependency. Beside higher scores on anxiety, depression, childhood trauma, aggression, and impulsivity, a larger proportion of dissociative group reported suicide attempts and self-mutilation than did the nondissociative group. Results of regression analyses suggest that severity of chronic anxiety, aggression (particularly hostility), and impulsivity were found to be mediators of association between childhood trauma and dissociation. Results suggest that, to reduce the risk of dissociation and related behavior such as suicide attempt and self-mutilation among substance dependents, chronic anxiety together with the feelings of hostility and impulsivity must be the targets of evaluation and treatment among those with history of childhood trauma.

Individual differences and social influences on the neurobehavioral pharmacology of abused drugs

The interaction of drugs with biologic targets is a critical area of research, particularly for the development of medications to treat substance use disorders. In addition to understanding these drug-target interactions, however, there is a need to understand more fully the psychosocial influences that moderate these interactions. The first section of this review introduces some examples from human behavioral pharmacology that illustrate the clinical importance of this research. The second section covers preclinical evidence to characterize some of the key individual differences that alter drug sensitivity and abuse vulnerability, related primarily to differences in response to novelty and impulsivity. Evidence is presented to indicate that critical neuropharmacological mechanisms associated with these individual differences involve integrated neurocircuits underlying stress, reward, and behavioral inhibitory processes. The third section covers social influences on drug abuse vulnerability, including effects experienced during infancy, adolescence, and young adulthood, such as maternal separation, housing conditions, and social interactions (defeat, play, and social rank). Some of the same neurocircuits involved in individual differences also are altered by social influences, although the precise neurochemical and cellular mechanisms involved remain to be elucidated fully. Finally, some speculation is offered about the implications of this research for the prevention and treatment of substance abuse.

Alcohol: the lubricant to suicidality

Suicide is a major public health problem in the United States as well as around the world. The significant role that alcohol plays in suicidality is well known and accepted in the scientific community. The use of alcohol does not necessarily lead to suicide, but through its action and effects, alcohol is an important proximal risk factor for suicidal behavior. There is very little data showing how and why alcohol exerts such tremendous influence and "lubricates the gears" to propel the act of committing suicide. This article will elucidate the complex relationship between alcohol and suicide and how alcohol use can lead to suicide. The article also describes how alcohol affects brain neurophysiology in regards to suicidal behavior.

Upregulated mRNA levels of SERT, NET, MAOB, and BDNF in various brain regions of ovariectomized rats exposed to chronic aversive stimuli

Estrogen deficiency increases the risk of anxiety and mood disorders, presumably by deranging metabolism of the monoamine neurotransmitters and the expression of their reuptake transporters in the brain. Although estrogen-deficient individuals were also susceptible to stress, little was known regarding the effect of stress on the levels of transcripts related to brain monoamine metabolism. Herein, we used quantitative real-time PCR to quantify the mRNA levels of serotonin reuptake transporter (SERT), norepinephrine transporter (NET), monoamine oxidase-B (MAOB), tryptophan hydroxylase (TPH), and tyrosine hydroxylase (TH) in various brain regions of ovariectomized (OVX) rats which had been exposed for 4 weeks to chronic aversive stimuli (CAS), such as water deprivation, cage tilt, and illumination. We found that CAS induced stress responses in OVX rats as indicated by increases in the adrenal gland weight and sucrose intake. After CAS exposure, mRNA levels of SERT and NET were upregulated in the frontal cortex, hippocampus, amygdala, and periaqueductal gray. In addition, CAS also increased the mRNA levels of MAOB, an enzyme for dopamine degradation, in the same brain regions. However, CAS did not alter the mRNA levels of TPH or TH, both of which are rate-limiting enzymes for the synthesis of serotonin and norepinephrine in the dorsal raphé and locus coeruleus, respectively. Interestingly, mRNA expression of brain-derived neurotrophic factor precursor was upregulated in the hippocampus of CAS-exposed OVX rats, suggesting a compensatory mechanism which might counteract the stress-induced depression. Therefore, the present data have provided evidence to explain how stress affected brain monoamine metabolism in estrogen-deficient stressed patients.

Deletion of CREB-regulated transcription coactivator 1 induces pathological aggression, depression-related behaviors, and neuroplasticity genes dysregulation in mice

BACKGROUND

Mood disorders are polygenic disorders in which the alteration of several susceptibility genes results in dysfunctional mood regulation. However, the molecular mechanisms underlying their transcriptional dysregulation are still unclear. The transcription factor cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) and the neurotrophin brain-derived neurotrophic factor (BDNF) have been implicated in rodent models of depression. We previously provided evidence that Bdnf expression critically rely on a potent CREB coactivator called CREB-regulated transcription coactivator 1 (CRTC1).

METHODS

To further evaluate the role of CRTC1 in the brain, we generated a knockout mouse line and analyzed its behavioral and molecular phenotype.

RESULTS

We found that mice lacking CRTC1 associate neurobehavioral endophenotypes related to mood disorders. Crtc1(-/-) mice exhibit impulsive aggressiveness, social withdrawal, and decreased sexual motivation, together with increased behavioral despair, anhedonia, and anxiety-related behavior in the novelty-induced hypophagia test. They also present psychomotor retardation as well as increased emotional response to stressful events. Crtc1(-/-) mice have a blunted response to the antidepressant fluoxetine in behavioral despair paradigms, whereas fluoxetine normalizes their aggressiveness and their behavioral response in the novelty-induced hypophagia test. Crtc1(-/-) mice strikingly show, in addition to a reduced dopamine and serotonin turnover in the prefrontal cortex, a concomitant decreased expression of several susceptibility genes involved in neuroplasticity, including Bdnf, its receptor TrkB, the nuclear receptors Nr4a1-3, and several other CREB-regulated genes.

CONCLUSIONS

Collectively, these findings support a role for the CRTC1-CREB pathway in mood disorders etiology and behavioral response to antidepressants and identify CRTC1 as an essential coactivator of genes involved in mood regulation.

Cases of adverse reaction to psychotropic drugs and possible association with pharmacogenetics

Thousands of samples for pharmacogenetic tests have been analysed in our laboratory since its establishment. In this article we describe some of the most interesting cases of CYP poor metabolisers associated with adverse reactions to psychotropic drugs. Prevention of disease/illness, including Adverse Drug Reaction (ADR), is an aim of modern medicine. Scientific data supports the fact that evaluation of drug toxicology includes several factors, one of which is genetic variations in pharmacodynamics and pharmacokinetics of drug pathways. These variations are only a part of toxicity evaluation, however, even if it would help to prevent only a small percentage of patients from suffering adverse drug reactions, especially life threatening ADRs, pharmacogenetic testing should play a significant role in any modern psychopharmacologic practice. Medical practitioners should also consider the use of other medications or alternative dosing strategies for drugs in patients identified as altered metabolisers. This will promise not only better and safer treatments for patients, but also potentially lowering overall healthcare costs.

Personality correlates of aggression: evidence from measures of the five-factor model, UPPS model of impulsivity, and BIS/BAS

Although many studies of personality and aggression focus on multidimensional traits and higher order personality disorders (e.g., psychopathy), lower order, unidimensional traits may provide more precision in identifying specific aspects of personality that relate to aggression. The current study includes a comprehensive measurement of lower order personality traits in relation to three forms of aggression: reactive, proactive, and relational. Traits related to interpersonal antagonism and impulsivity, especially impulsive behavior in the context of negative affect, were consistently related to aggression across multiple indices. These findings suggest that certain lower order traits are of critical importance to understanding who engages in aggressive behavior and why this behavior occurs.

Dopamine response to psychosocial stress in humans and its relationship to individual differences in personality traits

BACKGROUND

Previous studies have reported inter-individual variability in the dopamine (DA) response to stress. This variability might be related to individual differences in the vulnerability to experience the negative effect of stress.

OBJECTIVE

To investigate whether personality traits as measured by the revised NEO personality inventory explain variability in DA response to a psychosocial stress task.

METHODS

Eleven healthy adults, mean age of 26 ± 3.87 underwent two positron emission tomography (PET) scans using the dopamine D(2/3) agonist, [11C]-(+)-PHNO under a control and stress condition. The simplified reference tissue model (SRTM) was used to obtain [11C]-(+)-PHNO binding potential (BP(ND)). Stress-induced DA response was indexed as a percent change in [11C]-(+)-PHNO BP(ND) between control and stress conditions. The regions of interest were defined into D2-rich regions, which included the Associative and Sensorimotor Striatum (AST and SMST); D(2/3) mixed regions, which included the limbic striatum (LST) and globus pallidus (GP); and D3-rich region, which included the Substantia Nigra (SN).

RESULTS

Several personality traits within the Neuroticism and Openness to Experience domain were significantly correlated with blunted DA response to stress. Specifically, the Angry-Hostility, Vulnerability, and Depression trait were associated with blunted DA stress response in the AST (r = -0.645, p = 0.032), LST (r = -0.677, p = 0.022) and GP (r = -0.736, p = 0.010), respectively. The Openness to Values was correlated with a decreased DA release in the SN (r = -0.706, p = 0.015).

CONCLUSION

Variability in DA stress response might be related to individual differences in personality.

Symptomatological features of patients with and without Ecstasy use during their first psychotic episode

Background: Ecstasy use is generally chosen by adolescents and young adults for its entactogenic properties (the production of feelings of empathy, love, and emotional closeness to others.) Despite this desired and frequently realized outcome, Ecstasy use has often resulted in the genesis of psychotic symptoms and aggressive behaviors, particularly after chronic and/or intensive use. Methods: To explore the negative consequences of Ecstasy use and to examine the aggressive nature oftentimes seen in many Ecstasy users we employed a case-control study model. We compared, by means of validated psychometric tests, the psychopathological symptoms (BPRS), the aggressiveness (OAS) and the social adjustment (DSM-GAF) of psychotic patients with (n = 23) and without (n = 46) recent user of Ecstasy, during their first psychotic episode and hospitalization. All 23 Ecstasy users were Ecstasy users only. Results: Almost all of the psychotic symptoms were of similar severity in both groups. Blunted affect was milder in users than in non-users, whereas hostility and aggressive behavior was significantly more severe in users than in non-users. Conclusions: psychosis with a high level of aggressiveness and violence constitutes an important ‘side-effect’ that surely runs counter to the expected entactogenic action of Ecstasy. At a patient psycho-educational level, this study suggests that the use of Ecstasy may be counterproductive with respect to user expectations.

Association between the TPH1 A218C polymorphism and risk of mood disorders and alcohol dependence: evidence from the current studies

BACKGROUND

Several studies have assessed the association between genetic polymorphisms of tryptophan hydroxylase (TPH1) and risk of mood disorders and alcohol dependence, with controversial results. Our aim was to assess the association of TPH1 A218C polymorphism (rs1800532) with mood disorders, including major depressive disorder and bipolar disorder, and alcohol dependence by using meta-analysis.

METHODS

Data were collected from the related literatures published until November 25, 2010 from MEDLINE, EMBASE and ISI Web of Science databases, and meta-analysis stratified by ethnicity was performed in either fixed or random effect model as appropriate by using Stata Statistical Package (version 10.0).

RESULTS

Twenty-seven individual studies were included in the current study, among which, there were 9 studies for bipolar disorder, with 1951 cases and 2161 controls, 14 studies for major depressive disorder, with 2340 cases and 3204 controls, and 4 studies for alcohol dependence, with 601 cases and 711 controls. We found that in Caucasian population, the TPH1 218AA genotype was significantly associated with increased bipolar disorder risk (recessive comparison: OR, 1.42; Bonferroni-adjusted P=0.006; homozygote comparison: OR, 1.63; Bonferroni-adjusted P=0.072), and elevated alcohol dependence risk (recessive comparison: OR, 1.83; Bonferroni-adjusted P=0.012), while the association was not significant in Asian population. Moreover, the A218C polymorphism did not appear to have any effect on major depressive disorder risk either in Caucasians or in Asians.

CONCLUSION

The TPH1 A218C polymorphism is a potential biomarker for bipolar disorder and alcohol dependence risk in Caucasian population.

Modulation of frontostriatal interaction aligns with reduced primary reward processing under serotonergic drugs

Recently, functional interactions between anteroventral prefrontal cortex and nucleus accumbens (NAcc) have been shown to relate to behavior counteracting reward-desiring (Diekhof and Gruber, 2010). Downregulation of the reward system by serotonin has also been suggested as the mode of action accounting for unsatisfactory effects of serotonin reuptake inhibitors (SSRIs) such as insufficient alleviation or even increase of anhedonia, and loss of interest. However, understanding of the in vivo mechanisms of SSRI-related alteration of the human reward system is still incomplete. Using functional magnetic resonance imaging (fMRI) within a double-blind cross-over within-subjects study design and administering the SSRI paroxetine, the dopamine/norepinephrine reuptake inhibitor bupropione, and placebo for 7 d each, we investigated a group of 18 healthy male subjects. Under paroxetine, subjects showed significantly decreased activation of the bilateral NAcc during processing of primary rewards (erotic videos), but not under bupropion. Similar to the previous study, analysis of psychophysiological interactions revealed that this downregulation relied on negative interactions between left and right NAcc fMRI signals and the bilateral anteroventral prefrontal cortex that now were significantly enhanced under paroxetine and reduced under bupropion. Individual drug-dependent modulations of interacting brain regions were significantly associated with individual expressions of impulsivity as a personality trait. Our results corroborate and extend previous insights on interregional crosstalk from secondary to primary rewards and demonstrate parallels between active inhibitory control of and serotonergic effects on the dopaminergic reward system's activity.

The psychopharmacology of aggressive behavior: a translational approach: part 1: neurobiology

Patients with mental disorders are at an elevated risk for developing aggressive behavior. In the last 19 years, the psychopharmacological treatment of aggression has changed dramatically because of the introduction of atypical antipsychotics into the market and the increased use of anticonvulsants and lithium in the treatment of aggressive patients.Using a translational medicine approach, this review (part 1 of 2) examines the neurobiology of aggression, discussing the major neurotransmitter systems implicated in its pathogenesis, namely, serotonin, glutamate, norepinephrine, dopamine, and γ-aminobutyric acid, and also their respective receptors. The preclinical and clinical pharmacological studies concerning the role of these neurotransmitters have been reviewed, as well as research using transgenic animal models. The complex interaction among these neurotransmitters occurs at the level of brain areas and neural circuits such as the orbitoprefrontal cortex, anterior cortex, amygdala, hippocampus, periaqueductal gray, and septal nuclei, where the receptors of these neurotransmitters are expressed. The neurobiological mechanism of aggression is important to understand the rationale for using atypical antipsychotics, anticonvulsants, and lithium in treating aggressive behavior. Further research is necessary to establish how these neurotransmitter systems interact with brain circuits to control aggressive behavior at the intracellular level.

The dopaminergic system and aggression in laying hens

The dopaminergic system is involved in the regulation of aggression in many species, especially via dopamine (DA) D1 and D2 receptor pathways. To investigate heritable differences in this regulation, 2 high aggressive strains [Dekalb XL (DXL) and low group egg productivity and survivability (LGPS)] and one low aggressive strain (low group egg productivity and survivability; HGPS) of laying hens were used in the study. The HGPS and LGPS lines were diversely selected using group selection for high and low group production and survivability. The DXL line is a commercial line selected through individual selection based on egg production. Heritable differences in aggressive propensity between the strains have been previously assessed. The birds were pair housed within the same strain and labeled as dominant or subordinate based on behavioral observation. For both experiments 1 and 2, behavioral analysis was performed on all 3 strains whereas neurotransmitter analysis was performed only on the most aggressive (DXL) and least aggressive (HGPS) strains. In experiment 1, the subordinate birds were treated with D1 agonist, D2 agonist, or saline controls (n = 12). In experiment 2, the dominant birds from a separate flock were treated with D1 antagonist, D2 antagonist, or saline controls (n = 12). Treatment-associated changes in aggressive behaviors and central neurotransmitters were measured. Aggression was increased in all strains in response to D1 agonism but increased only in the less aggressive HGPS birds with D2 agonism. Aggression was decreased and hypothalamic serotonin and epinephrine were increased in birds from all strains treated with D2 receptor antagonist. The D1 receptor antagonism elicited different behavioral and neurotransmitter responses based on the aggressive phenotype of the genetic strains. Aggressive strains DXL and LGPS but not the HGPS strain decreased aggressiveness following antagonism of the D1 receptor. The data show evidence for distinct neurotransmitter regulation of aggression in high and low aggressive strains of hens through different receptor systems. These chicken lines could provide new animal models for the biomedical investigation of the genetic basis of aggression.

Toxoplasma gondii antibody titers and history of suicide attempts in patients with schizophrenia

Toxoplasma gondii (T. gondii) a widespread neurotropic parasite, has been previously associated with schizophrenia and more recently with suicidal behavior. However, no previous study has examined the association of T. gondii with suicidal behavior in schizophrenia patients. 950 individuals diagnosed with schizophrenia by SCID were recruited from the Munich area of Germany. Solid-enzyme immunoassay methods were used to measure IgG plasma antibodies to T. gondii, other neurotropic pathogens and gliadin. Logistic regression models were developed to analyze the association of T. gondii seropositivity or serointensity with history of suicidal behavior. In those younger than the median age of the sample, 38, T. gondii serointensity was associated with history of suicidal behavior (p = 0.02), while in the older patients the relationship was not significant (p = 0.21). Seropositivity was also associated with history of suicide attempt in younger patients, odds ratio 1.59 (95% CI 1.06 to 2.40), p = 0.03. Seropositivity for CMV (p = 0.22), HSV-1 (p = 0.36) and gliadin (p = 0.92) was not related to history of suicide attempt in the entire sample or any age subgroup. T. gondii serology might become, with interaction with vulnerability genes, a candidate biomarker for a subgroup of schizophrenia patients prone to attempting suicide.

Temporal and frontal lobe initiation and regulation of the top-down escalation of anger and aggression

The widespread, across-species strategy of stagewise escalation of aggression in agonistic encounters can be understood in terms of resource capture and control with least risk and cost. Human anger likely follows similar principles. As an adaptive phenomenon, escalation may involve particular neural circuitry. To advance beyond a standard view that the frontal lobe tonically inhibits subcortical circuits of aggression, a model is proposed which starts with the general rostrally directed flow of information in the brain. Earlier stage processing of visual and auditory input is transmitted from posterior and middle temporal cortices to anterior temporal lobe where rudimentary appraisals of threat and provocation are developed. These directly but diffusely activate cortical/subcortical anger/aggression response systems. At the same time, the anterior temporal loci transmit the modality-specific perceptual information to orbito-frontal cortex where it is integrated with information about, e.g., the opponent's relative dominance/social status and evaluated for likelihood of potential rewards and punishments associated with different modes of responding and so forth. These frontal areas then impose an inhibitory gating or modulation and focusing of activity initiated by the anterior temporal loci through their projections to GABAergic interneurons in the same cortical/subcortical circuits. Escalation occurs as the inhibition imposed by the frontal areas is progressively lifted. Exploration of the implications, applications and hypotheses flowing from this model will improve our understanding of the biologically important and socially significant phenomena of escalation.

Mood and personality effects in healthy participants after chronic administration of sertraline

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) are utilised in the treatment of a wide range of disorders but the neuropsychological basis of their therapeutic efficacy remains unclear. In this study we examine the impact of 3 weeks administration of sertraline, an SSRI, on mood and personality in a group of healthy volunteers to understand the effect of these agents in the absence of clinical disorder.

METHODS

Thirty-eight healthy women and men, with no personal or familial history of Axis I disorder were randomised to receive either a placebo or sertraline (50mg/day p.o.) for an average of 23 days, in a double-blind design. Self-report indices of mood and personality, and genotype (5-HTTLPR) and sertraline bioavailability were assessed.

RESULTS

Chronic administration of an SSRI was found to alter mood and personality. The SSRI group experienced a significant decrease in negative affect (NA), guilt and attentiveness, and significant increases in positive affect (PA), joviality, self-assurance and serenity. Genotype and bioavailability of sertraline did not moderate these findings, however gender did. Only females demonstrated increased PA and joviality, and decreased NA; whereas, only males demonstrated decreased attentiveness.

LIMITATIONS

Greater power and a more specific manipulation of serotonergic functioning would help clarify the neurochemical basis of these findings.

CONCLUSIONS

Results from the current study demonstrate that longer term administration of SSRIs alters aspects of mood and personality in the absence of disorder. This suggests that these agents have effects on basic psychological processes that may in turn form the basis of their therapeutic efficacy.

Effects of lowered serotonin transmission on cocaine-induced striatal dopamine response: PET [¹¹C]raclopride study in humans

BACKGROUND

Low serotonin transmission is thought to increase susceptibility to a wide range of substance use disorders and impulsive traits.

AIMS

To investigate the effects of lowered serotonin on cocaine-induced (1.0 mg/kg cocaine, self-administered intranasally) dopamine responses and drug craving.

METHOD

In non-dependent cocaine users, serotonin transmission was reduced using the acute tryptophan depletion method. Striatal dopamine responses were measured using positron emission tomography with [(11)C]raclopride.

RESULTS

Acute tryptophan depletion increased drug craving and striatal dopamine responses to cocaine. These acute tryptophan depletion-induced increases did not occur in the absence of cocaine.

CONCLUSIONS

The results suggest that low serotonin transmission can increase dopaminergic and appetitive responses to cocaine. These findings might identify a mechanism by which individuals with low serotonin are at elevated risk for both substance use disorders and comorbid conditions.

The influence of sex-linked genetic mechanisms on attention and impulsivity

It is now generally agreed that there are inherent sex differences in healthy individuals across a number of neurobiological domains (including brain structure, neurochemistry, and cognition). Moreover, there is a burgeoning body of evidence highlighting sex differences within neuropsychiatric populations (in terms of the rates of incidence, clinical features/progression, neurobiology and pathology). Here, we consider the extent to which attention and impulsivity are sexually dimorphic in healthy populations and the extent to which sex might modulate the expression of disorders characterised by abnormalities in attention and/or impulsivity such as attention deficit hyperactivity disorder (ADHD), autism and addiction. We then discuss general genetic mechanisms that might underlie sex differences in attention and impulsivity before focussing on specific positional and functional candidate sex-linked genes that are likely to influence these cognitive processes. Identifying novel sex-modulated molecular targets should ultimately enable us to develop more effective therapies in disorders associated with attentional/impulsive dysfunction.

Altered tryptophan and alanine transport in fibroblasts from boys with attention-deficit/hyperactivity disorder (ADHD): an in vitro study

Background

The catecholaminergic and serotonergic neurotransmitter systems are implicated in the pathophysiology of attention-deficit/hyperactivity disorder (ADHD). The amino acid tyrosine is the precursor for synthesis of the catecholamines dopamine and norepinephrine, while tryptophan is the precursor of serotonin. A disturbed transport of tyrosine, as well as other amino acids, has been found in a number of other psychiatric disorders, such as schizophrenia, bipolar disorder and autism, when using the fibroblast cell model. Hence, the aim of this study was to explore whether children with ADHD may have disturbed amino acid transport.

Methods

Fibroblast cells were cultured from skin biopsies obtained from 14 boys diagnosed with ADHD and from 13 matching boys without a diagnosis of a developmental disorder. Transport of the amino acids tyrosine, tryptophan and alanine across the cell membrane was measured by the cluster tray method. The kinetic parameters, maximal transport capacity (V_max) and affinity constant (K_m) were determined. Any difference between the two groups was analyzed by Student's unpaired t-test or the Mann Whitney U test.

Results

The ADHD group had significantly decreased V_max (p = 0.039) and K_m (increased affinity) (p = 0.010) of tryptophan transport in comparison to controls. They also had a significantly higher V_maxof alanine transport (p = 0.031), but the Km of alanine transport did not differ significantly. There were no significant differences in any of the kinetic parameters regarding tyrosine transport in fibroblasts for the ADHD group.

Conclusions

Tryptophan uses the same transport systems in both fibroblasts and at the blood brain barrier (BBB). Hence, a decreased transport capacity of tryptophan implies that less tryptophan is being transported across the BBB in the ADHD group. This could lead to deficient serotonin access in the brain that might cause disturbances in both the serotonergic and the catecholaminergic neurotransmitter systems, since these systems are highly interconnected. The physiological importance of an elevated transport capacity of alanine to the brain is not known to date.

Suicide cases and venlafaxine

Piatkov I, Jones T, Van Vuuren RJ. Suicide cases and venlafaxine.

Objective: Our aim was to establish whether the presence or absence of fully functioning cytochrome P450 2D6, 2C19 and 2C9 genetic alleles was associated with suicide in patients receiving venlafaxine treatment.

Method: Authorisation from the NSW State Coroner to perform post-mortem genetic testing was obtained for 11 samples from deceased persons who committed suicide during treatment with venlafaxine (VENADR study).

Results: All patients, but one, have at least one copy of the loss-of-function, altered or decreased cytochrome P450 enzyme activity allele. Four patients' results reveal loss-of-function genotypes, while all others were found to have diminished enzyme activity polymorphisms. Seven patients had multiple altered function polymorphisms, which included CYP2D6, CYP2C19 or CYP2C9.

Conclusion: Our preliminary limited data show that neurotoxicity development, which manifests as suicide while on venlafaxine treatment, probably correlates with a higher prevalence of gene copies of altered functioning cytochrome P450 genetic polymorphisms.

Prescribed drugs and violence: a case/noncase study in the French PharmacoVigilance Database

AIM

Our aim was to identify prescribed drugs associated with violent behaviours using the French PharmacoVigilance Database (FPVD).

METHODS

All reports of adverse drug reactions (ADR) recorded in the FPVD between 1 January 1985 and 31 July 2008 and including the terms aggressiveness or violence were selected. We compared proportion of exposure to different drugs between cases (reports with violence) and noncases (other reports in the database).

RESULTS

Among 537 cases, 56 were included (48 men, mean age 46 years). Misuse was observed in ten cases (18%). In 25 cases (44.6%), a previous psychiatric history was documented. Main drugs involved were nervous system (63.6%) followed by respiratory (7.8%), alimentary tract and metabolism (7.8%), dermatological (5.2%) and anti-infective (5.2%) agents. Case/noncase analysis found an association with dopaminergic agonists (pergolide, pramipexole, bromocriptine, piribedil), benzodiazepines (alprazolam, bromazepam) and serotoninergic antidepressants (taken as a whole), but not antipsychotics or antiepileptics. Association was also found with varenicline, isotretinoin, interferon alpha-2b, rimonabant, benfluorex, topiramate and antiviral drugs (ribavirin, efavirenz).

CONCLUSION

Dopaminergic agonists, benzodiazepines and serotoninergic antidepressants are the main pharmacological classes able to induce aggressive behaviour. This study also emphasises the putative role of other drugs less known to be involved in such ADR.

The interaction between serotonin receptor 2A and catechol-O-methyltransferase gene polymorphisms is associated with the novelty-seeking subscale impulsiveness

OBJECTIVE

Novelty seeking is a trait that has been consistently associated with problem behaviours. There is evidence for heritability of novelty seeking, but the molecular genetic basis of the trait is still widely unclear.

METHODS

The interaction between polymorphisms of catechol-O-methyltransferase (COMT) and serotonin receptor 2A genes was examined in relation to novelty seeking and its different subscales in healthy Finnish adults. A subsample of 1214 participants derived from a population-based sample was genotyped for the COMT Val158Met (rs4680) and HTR2A T102C (rs6313) genes. Novelty seeking was measured twice, with a 4-year interval, using Cloninger's Temperament and Character Inventory.

RESULTS

The interaction between COMT Val158Met and HTR2A T102C polymorphisms was found to be associated with subscale impulsiveness. T/T carriers of HTR2A T102C polymorphism, that also had Met/Met genotype of COMT Val158Met single nucleotide polymorphism, scored significantly higher on impulsiveness than Val allele carriers (P=0.005).

CONCLUSION

Our results suggest that the interaction between dopaminergic and serotonergic genes might underlie impulsiveness. Together with earlier research our results also stress the importance of considering novelty seeking as a heterogeneous trait with its subscales having different genetic backgrounds.

Biological aspect of hyperthymic temperament: light, sleep, and serotonin

RATIONALE

Hyperthymic temperament is one of several premorbid temperaments putatively associated with bipolar disorder. Several reports suggest that depressive patients with hyperthymic temperament may belong to the proposed soft bipolar spectrum.

OBJECTIVES

To investigate biological aspects of hyperthymic temperament, the present study examined daily activity, sleep time, central serotonergic function, and other relevant variables in relation to hyperthymic temperament in healthy subjects.

METHODS

Fifty six healthy subjects were monitored via the actigraphy system to measure daily total activity, sleep time, and illuminance. A neuroendocrine challenge test was performed to estimate central serotonergic function.

RESULTS

Multiple regression analysis revealed that higher illuminance of daytime, greater fluctuation in sleep time, and lower central serotonergic function significantly and independently predicted hyperthymic temperament scores.

CONCLUSIONS

The present findings suggest that light, sleep, and serotonin are crucial factors in understanding hyperthymic temperament, which may be common to bipolar disorder.

Clarifying relations between dispositional aggression and brain potential response: overlapping and distinct contributions of impulsivity and stress reactivity

Impulsive-aggressive individuals exhibit deficits in amplitude of the P3 brain potential response, however, it remains unclear how separable dispositional traits account for this association. The current study sought to clarify the basis of this association by examining contributions of trait impulsiveness and stress reactivity to the observed relationship between dispositional aggression and amplitude of the P3 brain potential response in a visual novelty-oddball procedure. A significant negative association was found between aggressiveness and amplitude of P3 response to both target and novel stimuli over frontal-central scalp sites. Impulsivity showed a parallel inverse relationship with P3 amplitude, attributable to its overlap with dispositional aggression. In contrast, stress reactivity did not exhibit a zero-order association with P3 amplitude, but modestly predicted P3 in a positive direction after accounting for its overlap with aggression. Results are discussed in terms of their implications for individual difference variables and brain processes underlying impulsive-aggressive behavior.