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

Replication of rs300774, a genetic biomarker near ACP1, associated with suicide attempts in patients with schizophrenia: Relation to brain cholesterol biosynthesis

The aim of this study was to determine if three biomarkers for suicide attempts previously identified and replicated in a genome-wide association (GWAS) study of bipolar disorder (BD) suicide attempters also predicted suicide attempts in patients prospectively diagnosed with schizophrenia (SCZ) or schizoaffective disorder (SAD). 162 genetically-verified Caucasian patients with SCZ or SAD were phenotyped for presence (45.7%) or absence of a lifetime suicide attempt. Three single nucleotide polymorphisms (SNPs) were genotyped or partially imputed from a GWAS dataset. After controlling for genetic architecture and gender, we replicated rs300774 (p = 0.012), near ACP1 (acid phosphatase 1), the top predictor of suicide attempts in the BD study. The result of Willour et al. (2012) was replicated in males (p = 0.046) but not in females (p = 0.205). The other two SNPs, rs7296262, and rs10437629, were not associated with suicide attempts in this study. rs300774 could be a cis-eQTL for ACP1, with minor allele carriers having lower expression levels (p = 0.002). This SNP also functioned as a trans-eQTL for genes related to cholesterol biosynthesis and the wnt-β-catenin pathway (p ≤ 0.0001). Further, co-expression analysis of candidate genes in brain suggested ACP1 is important to the regulation of a number of brain mechanisms linked to suicide, including cholesterol synthesis, β-catenin-mediated signaling pathway, serotonin, GABA, and the stress response via ARHGAP35 (p190rhogap), a repressor of glucocorticoid receptor (NR3C1) transcription. This study provides an additional validation of rs300774 as a potential transdiagnostic biomarker for suicide attempts and evidence that ACP1 may have an important role in regulation of the multiple systems associated with suicide.

Pilot study indicate role of preferentially transmitted monoamine oxidase gene variants in behavioral problems of male ADHD probands

Background

Attention deficit hyperactivity disorder (ADHD) is an etiologically complex childhood onset neurobehavioral disorder characterized by age-inappropriate inattention, hyperactivity, and impulsivity. Symptom severity varies widely and boys are diagnosed more frequently than girls. ADHD probands were reported to have abnormal transmissions of dopamine, serotonin, and/or noradrenaline. Monoamine oxidase A (MAOA) and B (MAOB), mitochondrial outer membrane bound two isoenzymes, mediate degradation of these neurotransmitters and thus regulating their circulating levels. Case-control analyses in different populations, including Indians, suggested involvement of MAOA and MAOB genes in the etiology of ADHD. Due to high heritability rate of ADHD, we tested familial transmission of MAOA and MAOB variants to ADHD probands in 190 nuclear families having ADHD probands from Indo-Caucasoid ethnicity.

Methods

Subjects were recruited following the Diagnostic and Statistical Manual of Mental Disorders-4th edition (DSM-IV). Appropriate scales were used for measuring the behavioral traits in probands. Genotyping was performed through PCR-based amplification of target sites followed by DNA-sequencing and/or gel-electrophoresis. Data obtained were analyzed by family based statistical methods.

Results

Out of 58 variants present in the analyzed sites only 15 were found to be polymorphic (30 bp-uVNTR, rs5906883, rs1465107, rs1465108, rs5905809, rs5906957, rs6323, rs1137070 from MAOA and rs4824562, rs56220155, rs2283728, rs2283727, rs3027441, rs6324, rs3027440 from MAOB). Statistically significant maternal transmission of alleles to male probands was observed for MAOA rs5905809 ‘G’ (p = 0.04), rs5906957 ‘A’ (p = 0.04), rs6323 ‘G’ (p = 0.0001) and MAOB rs56220155 ‘A’ (p = 0.002), rs2283728 ‘C’ (p = 0.0008), rs2283727 ‘C’ (p = 0.0008), rs3027441 ‘T’ (p = 0.003), rs6324 ‘C’ (p = 0.003), rs3027440 ‘T’ (p = 0.0002). Significantly preferential maternal transmissions of different haplotype combinations to male probands were also noticed (p < 0.05), while female probands did not reveal such transmission bias. Behavioral traits of male probands exhibited significant association with gene variants. Age of the mother at pregnancy also revealed association with risk variants of male probands.

Conclusions

It may be inferred that the MAOA and MAOB variants may contribute to the etiology of ADHD in the Indo-Caucasoid population and could be responsible for higher occurrence of ADHD in the boys.

Electronic supplementary material

The online version of this article (10.1186/s12881-017-0469-5) contains supplementary material, which is available to authorized users.

The Role of Anabolic Androgenic Steroids in Disruption of the Physiological Function in Discrete Areas of the Central Nervous System

Anabolic-androgenic steroids (AAS) abuse is often associated with a wide spectrum of adverse effects. These drugs are frequently abused by adolescents and athletes for esthetic purposes, as well as for improvement of their endurance and performances. In this literature review, we evaluated the correlation between AAS and anxiety or aggression. Two pathways are thought to be involved in AAS-induced behavioral disorders. Direct pathway via the amygdalo-fugal pathway, which connects the central nucleus of the amygdala to the brainstem, is involved in cognitive-emotive and homeostatic processes. The latter is modified by chronic AAS use, which subsequently leads to increased anxiety. Indirect pathways via the serotonergic, dopaminergic, and glutamatergic signals which are modified by AAS abuse in latero-anterior hypothalamus and can mediate the aggressive behavior. In conclusion, the molecular mechanisms underlying the behavioral alterations following AAS abuse is unclear and remains ambiguous as additional long-term studies aimed to understand the precise mechanisms are required.

Metabolomics for Plant Improvement: Status and Prospects

Post-genomics era has witnessed the development of cutting-edge technologies that have offered cost-efficient and high-throughput ways for molecular characterization of the function of a cell or organism. Large-scale metabolite profiling assays have allowed researchers to access the global data sets of metabolites and the corresponding metabolic pathways in an unprecedented way. Recent efforts in metabolomics have been directed to improve the quality along with a major focus on yield related traits. Importantly, an integration of metabolomics with other approaches such as quantitative genetics, transcriptomics and genetic modification has established its immense relevance to plant improvement. An effective combination of these modern approaches guides researchers to pinpoint the functional gene(s) and the characterization of massive metabolites, in order to prioritize the candidate genes for downstream analyses and ultimately, offering trait specific markers to improve commercially important traits. This in turn will improve the ability of a plant breeder by allowing him to make more informed decisions. Given this, the present review captures the significant leads gained in the past decade in the field of plant metabolomics accompanied by a brief discussion on the current contribution and the future scope of metabolomics to accelerate plant improvement.

Crop-damaging temperatures increase suicide rates in India

More than three quarters of the world's suicides occur in developing countries, yet little is known about the drivers of suicidal behavior in poor populations. I study India, where one fifth of global suicides occur and suicide rates have doubled since 1980. Using nationally comprehensive panel data over 47 y, I demonstrate that fluctuations in climate, particularly temperature, significantly influence suicide rates. For temperatures above 20 °C, a 1 °C increase in a single day's temperature causes ∼70 suicides, on average. This effect occurs only during India's agricultural growing season, when heat also lowers crop yields. I find no evidence that acclimatization, rising incomes, or other unobserved drivers of adaptation are occurring. I estimate that warming over the last 30 y is responsible for 59,300 suicides in India, accounting for 6.8% of the total upward trend. These results deliver large-scale quantitative evidence linking climate and agricultural income to self-harm in a developing country.

The Cathinones MDPV and α-PVP Elicit Different Behavioral and Molecular Effects Following Acute Exposure

Since the mid-to-late 2000s, synthetic cathinones have gained popularity among drug users due to their psychostimulant effects greater than those produced by cocaine and amphetamine. Among them, 3,4-methylenedioxypyrovalerone (MDPV) and 1-phenyl-2-(pyrrolidin-1-yl)pentan-1-one (α-PVP) are ones of the most popular cathinones available in the clandestine market as "bath salts" or "fertilizers." Pre-clinical studies indicate that MDPV and α-PVP induced psychomotor stimulation, affected thermoregulation, and promoted reinforcing properties in rodents. However, a direct comparative analysis on the effects caused by MDPV and α-PVP on the behavior and neuronal activation in rodents is still lacking. Behavioral analyses revealed that both MDPV and α-PVP affect spontaneous and stimulated motor responses. In particular, MDPV showed a greater psychomotor effect than α-PVP in line with its higher potency in blocking the dopamine transporter (DAT). Notably, MDPV was found to be more effective than α-PVP in facilitating spontaneous locomotion and it displayed a biphasic effect in contrast to the monophasically stimulated locomotion induced by α-PVP. In addition to the behavioral results, we also found a different modulation of immediate early genes (IEGs) such as Arc/Arg3.1 and c-Fos in the frontal lobe, striatum, and hippocampus, indicating that these drugs do impact brain homeostasis with changes in neuronal activity that depend on the drug, the brain area analyzed, and the timing after the injection. These results provide the first discrimination between MDPV and α-PVP based on behavioral and molecular data that may contribute to explain, at least in part, their toxicity.

Impulse Control and Related Disorders in Parkinson's Disease

Impulse control disorders (ICDs), such as compulsive gambling, buying, sexual, and eating behaviors, are a serious and increasingly recognized complication in Parkinson's disease (PD), occurring in up to 20% of PD patients over the course of their illness. Related behaviors include punding (stereotyped, repetitive, purposeless behaviors), dopamine dysregulation syndrome (DDS) (compulsive medication overuse), and hobbyism (e.g., compulsive internet use, artistic endeavors, and writing). These disorders have a significant impact on quality of life and function, strain interpersonal relationships, and worsen caregiver burden, and are associated with significant psychiatric comorbidity. ICDs have been most closely related to the use of dopamine agonists (DAs), while DDS is primarily associated with shorter acting, higher potency dopamine replacement therapy (DRT), such as levodopa. However, in preliminary research ICDs have also been reported to occur with monoamine oxidase inhibitor-B and amantadine treatment, and after deep brain stimulation (DBS) surgery. Other risk factors for ICDs may include sex (e.g., male sex for compulsive sexual behavior, and female sex for compulsive buying behavior); younger age overall at PD onset; a pre-PD history of an ICD; personal or family history of substance abuse, bipolar disorder, or gambling problems; and impulsive personality traits. Dysregulation of the mesocorticolimbic dopamine system is thought to be the major neurobiological substrate for ICDs in PD, but there is preliminary evidence for alterations in opiate and serotonin systems too. The primary treatment of ICDs in PD is discontinuation of the offending treatment, but not all patients can tolerate this due to worsening motor symptoms or DA withdrawal syndrome. While psychiatric medications and psychosocial treatments are frequently used to treat ICDs in the general population, there is limited empirical evidence for their use in PD, so it is critical for patients to be monitored closely for ICDs from disease onset and routine throughout its course. In the future, it may be possible to use a precision medicine approach to decrease the incidence of ICDs in PD by avoiding DA use in patients determined to be at highest risk based on their clinical and neurobiological (e.g., motor presentation, behavioral measures of medication response, genetics, dopamine transporter neuroimaging) profile. Additionally, as empirically validated treatments for ICDs and similar disorders (e.g., substance use disorders) emerge, it will also be important to examine their efficacy and tolerability in individuals with comorbid PD.

Music genetics research: Association with musicality of a polymorphism in the AVPR1A gene

Musicality is defined as a natural tendency, sensibility, knowledge, or talent to create, perceive, and play music. Musical abilities involve a great range of social and cognitive behaviors, which are influenced by both environmental and genetic factors. Although a number of studies have yielded insights into music genetics research, genes and biological pathways related to these traits are not fully understood. Our hypothesis in the current study is that genes associated with different behaviors could also influence the musical phenotype. Our aim was to investigate whether polymorphisms in six genes (AVPR1A, SLC6A4, ITGB3, COMT, DRD2 and DRD4) related to social and cognitive traits are associated with musicality in a sample of children. Musicality was assessed through an individualized music therapy assessment profile (IMTAP) which has been validated in Brazil to measure musical ability. We show here that the RS1 microsatellite of the AVPR1A gene is nominally associated with musicality, corroborating previous results linking AVPR1A with musical activity. This study is one of the first to investigate musicality in a comprehensive way, and it contributes to better understand the genetic basis underlying musical ability.

Impulse Control Disorders and Related Complications of Parkinson's Disease Therapy

Impulsive and compulsive behaviors in Parkinson's disease (PD) patients are most often attributed to dopamine agonist therapy; dysregulation of the mesocorticolimbic system accounts for this behavioral phenotype. The clinical presentation is commonly termed impulse control disorder (ICD): Behaviors include hypersexuality, compulsive eating, shopping, pathological gambling, and compulsive hobby participation. However, not all PD individuals taking dopamine agonists develop these behavioral changes. In this review, the authors focus on the similarities between the phenotypic presentation of ICDs with that of other reward-based behavioral disorders, including binge eating disorder, pathological gambling, and substance use disorders. With this comparison, we emphasize that the transition from an impulsive to compulsive behavior likely follows a ventral to dorsal striatal pattern, where an altered dopaminergic reward system underlies the emergence of these problematic behaviors. The authors discuss the neurobiological similarities between these latter disorders and ICDs, emphasizing similar pathophysiological processes and discussing treatment options that have potential for translation to PD patients.

An emerging role for the lateral habenula in aggressive behavior

Inter-male aggression is an essential component of social behavior in organisms from insects to humans. However, when expressed inappropriately, aggression poses significant threats to the mental and physical health of both the aggressor and the target. Inappropriate aggression is a common feature of numerous neuropsychiatric disorders in humans and has been hypothesized to result from the atypical activation of reward circuitry in response to social targets. The lateral habenula (LHb) has recently been identified as a major node of the classical reward circuitry and inhibits the release of dopamine from the midbrain to signal negative valence. Here, we discuss the evidence linking LHb function to aggression and its valence, arguing that strong LHb outputs to the ventral tegmental area (VTA) and the dorsal raphe nucleus (DRN) are likely to play roles in aggression and its rewarding components. Future studies should aim to elucidate how various inputs and outputs of the LHb shape motivation and reward in the context of aggression.

Evaluation of Cholesterol as a Biomarker for Suicidality in a Veteran Sample

A reduction in total cholesterol may alter the microviscosity of the brain-cell-membrane, reducing serotonin receptor exposure. The resulting imbalance between serotonin and dopamine may lead to an increased risk for suicidality. The objective of this research was to evaluate total cholesterol as a biological marker for suicidality in a sample of US military veterans. The study population consisted of veterans who received care at the Coatesville Veterans Affairs Medical Center (VAMC) and were included in the Suicide Prevention Coordinator's database for having suicidal ideation with evidence of escalating intent, a documented suicide attempt, or committed suicide between 2009 and 2015. The veterans' medical data were obtained from the facility's computerized patient record system. The final sample was 188 observations from 128 unique veterans. Veterans with total cholesterol levels below 168 mg/dl appeared to have a higher suicide risk than those with higher levels. The cholesterol levels of veterans reporting suicidal ideation or attempt were significantly lower than the group reporting neither [F(2, 185) = 30.19, p < .001]. When data from multiple visits were available, veterans reporting suicidal ideation or attempt had experienced a significant (20%) decrease in cholesterol levels from an earlier visit in which they did not report suicidality. A latent class analysis revealed that among other differences, suicidal veterans were younger, leaner, and had more anxiety, sleep problems, and higher education than those being seen for an issue unrelated to suicidality. © 2017 Wiley Periodicals, Inc.

Trait Impulsivity and the Externalizing Spectrum

This article reviews evidence that trait impulsivity-expressed early in life as the hyperactive-impulsive and combined presentations of attention-deficit/hyperactivity disorder (ADHD)-is a bottom-up, subcortically mediated vulnerability to all externalizing disorders. This vulnerability arises from deficient mesolimbic dopamine responding, which imbues psychological states (irritability, discontentment) that motivate excessive approach behavior (hyperactivity, impulsivity). Through complex interactions with (a) aversive motivational states that arise from largely independent subcortical systems, (b) emotion regulatory mechanisms that arise from top-down, cortical modulation of subcortical neural function, and (c) environmental risk factors that shape and maintain emotion dysregulation, trait impulsivity confers vulnerability to increasingly severe externalizing behaviors across development. This perspective highlights the importance of identifying transdiagnostic neural vulnerabilities to psychopathology; dovetails with the hierarchical, latent structure of psychopathology; and suggests that progression along the externalizing spectrum is an ontogenic process whereby a common, multifactorially inherited trait interacts with endogenous and exogenous influences to yield increasingly intractable externalizing behaviors across development.

Differential effects of cannabinoid CB1 inverse agonists and antagonists on impulsivity in male Sprague Dawley rats: identification of a possibly clinically relevant vulnerability involving the serotonin 5HT1A receptor

RATIONALE

Cannabinoid CB1 inverse agonists hold therapeutic promise as appetite suppressants but have produced suicidal behaviors among a small subpopulation in clinical trials. Anatomical and pharmacological evidence implicate the 5HT_1A serotonin receptor in suicide in humans and impulsivity in humans and animals.

OBJECTIVE

The objective of the study is to assess whether 5HT_1A blockade is necessary for CB1 ligands to produce impulsivity.

METHODS

Sprague Dawley rats were administered the CB1 inverse agonist AM 251, the CB1 antagonist AM 6527, or the peripherally restricted antagonist AM 6545, with or without pretreatment with the 5HT_1A antagonist WAY 100,635 (WAY) on the paced fixed consecutive number (FCN) task, which measures choice to terminate a chain of responses prematurely. As FCN is sensitive to changes in time perception, which have been demonstrated with CB1 blockade, a novel variable consecutive number task with discriminative stimulus (VCN-S _D ) was also performed and proposed to be less sensitive to changes in timing.

RESULTS

Pretreatment with WAY enabled mild but significant reductions in FCN accuracy for AM 251 and AM 6527. No effects were found for AM 6545. On the VCN-S _D task, substantial impairments were found for the combination of WAY and AM 251.

CONCLUSIONS

AM 251, but not the antagonists AM 6527 or AM 6545, produced impulsivity only following systemic 5HT_1A blockade. Although preliminary, the results may indicate that disrupted serotonin signaling produces a vulnerability to undesirable effects of CB1 inverse agonists, which is not evident in the general population. Furthermore, neutral CB1 antagonists do not produce this effect and therefore may have greater safety.

Lurasidone for the Treatment of Irritability Associated with Autistic Disorder

The aim of this study was to evaluate the short-term efficacy and safety of lurasidone in treating irritability associated with autistic disorder. In this multicenter trial, outpatients age 6–17 years who met DSM-IV-TR criteria for autistic disorder, and who demonstrated irritability, agitation, and/or self-injurious behaviors were randomized to 6 weeks of double-blind treatment with lurasidone 20 mg/day (N = 50), 60 mg/day (N = 49), or placebo (N = 51). Efficacy measures included the Aberrant Behavior Checklist Irritability subscale (ABC-I, the primary endpoint) and the Clinical Global Impressions, Improvement (CGI-I) scale, and were analyzed using a likelihood-based mixed model for repeated measures. Least squares (LS) mean (standard error [SE]) improvement from baseline to Week 6 in the ABC-I was not significantly different for lurasidone 20 mg/day (−8.8 [1.5]) and lurasidone 60 mg/day (−9.4 [1.4]) versus placebo (−7.5 [1.5]; p = 0.55 and 0.36, respectively). CGI-I scores showed significantly greater LS mean [SE] improvement at Week 6 for lurasidone 20 mg/day versus placebo (2.8 [0.2] vs. 3.4 [0.2]; p = 0.035) but not for lurasidone 60 mg/day (3.1 [0.2]; p = 0.27). Discontinuation rates due to adverse events were: lurasidone 20 mg/day, 4.1 %; 60 mg/day, 3.9 %; and placebo, 8.2 %. Adverse events with an incidence ≥10 % (lurasidone combined, placebo) included vomiting (18.0, 4.1 %) and somnolence (12.0, 4.1 %). Modest changes were observed in weight and selected metabolic parameters. In this study, once-daily, fixed doses of 20 and 60 mg/day of lurasidone were not demonstrated to be efficacious compared to placebo for the short-term treatment of children and adolescents with moderate-to-severe irritability associated with autistic disorder.

Auditory evoked potential could reflect emotional sensitivity and impulsivity

Emotional sensitivity and impulsivity could cause interpersonal conflicts and neuropsychiatric problems. Serotonin is correlated with behavioral inhibition and impulsivity. This study evaluated whether the loudness dependence of auditory evoked potential (LDAEP), a potential biological marker of central serotonergic activity, could reflect emotional sensitivity and impulsivity. A total of 157 healthy individuals were recruited, who performed LDAEP and Go/Nogo paradigms during electroencephalogram measurement. Barratt impulsivity scale (BIS), Conners’ Adult ADHD rating scale (CAARS), and affective lability scale (ALS) were evaluated. Comparison between low and high LDAEP groups was conducted for behavioural, psychological, and event-related potential (ERP) measures. The high LDAEP group showed significantly increased BIS, a subscale of the CAARS, ALS, and false alarm rate of Nogo stimuli compared to the low LDAEP group. LDAEP showed significant positive correlations with the depression scale, ALS scores, subscale of the CAARS and Nogo-P3 amplitude. In the source activity of Nogo-P3, the cuneus, lingual gyrus, and precentral gyrus activities were significantly increased in the high LDAEP group. Our study revealed that LDAEP could reflect emotional sensitivity and impulsivity. LDAEP, an auditory evoked potential could be a useful tool to evaluate emotional regulation.

Psychopharmacology of Persistent Violence and Aggression

Persistent violence not due to acute psychosis or mania can be managed only after appropriate characterization of the aggressive episodes (psychotic, impulsive, or predatory/planned/instrumental). The type of violence combined with the psychiatric diagnosis dictates the evidence-based pharmacologic approaches for psychotically motivated and impulsive aggression, whereas instrumental violence mandates forensic/behavioral strategies. For nonacute inpatients, schizophrenia spectrum disorders, traumatic brain injury, and dementia comprise the majority of individuals who are persistently aggressive, with impulsive actions the most common form of violence across all diagnoses. Neurobiological considerations combined with empirical data provide a comprehensive framework for systematic medication trials to manage persistently aggressive patients.

Reward vs. Retaliation-the Role of the Mesocorticolimbic Salience Network in Human Reactive Aggression

The propensity for reactive aggression (RA) which occurs in response to provocation has been linked to hyperresponsivity of the mesocorticolimbic reward network in healthy adults. Here, we aim to elucidate the role of the mesocorticolimbic network in clinically significant RA for two competing motivated behaviors, reward-seeking vs. retaliation. 18 male participants performed a variant of the Point-Subtraction Aggression Paradigm (PSAP) during functional magnetic resonance imaging (fMRI). We examined whether RA participants compared with non-aggressive controls would choose to obtain a monetary reward over the opportunity to retaliate against a fictitious opponent, who provoked the participant by randomly stealing money from his earnings. Across all fMRI-PSAP runs, RA individuals vs. controls chose to work harder to earn money but not to retaliate. When engaging in such reward-seeking behavior vs. retaliation in a single fMRI-PSAP run, RA individuals exhibited increased activation in the insular-striatal part of the mesocorticolimbic salience network, and decreased precuneus and ventromedial prefrontal cortex activation compared to controls. Enhanced overall reward-seeking behavior along with an up-regulation of the mesocorticolimbic salience network and a down-regulation of the default-mode network in RA individuals indicate that RA individuals are willing to work more for monetary reward than for retaliation when presented with a choice. Our findings may suggest that the use of positive reinforcement might represent an efficacious intervention approach for the potential reduction of retaliatory behavior in clinically significant RA.

The Role of the Catechol-o-Methyltransferase (COMT) GeneVal158Met in Aggressive Behavior, a Review of Genetic Studies

Aggressive behaviors have become a major public health problem, and early-onset aggression can lead to outcomes such as substance abuse, antisocial personality disorder among other issues. In recent years, there has been an increase in research in the molecular and genetic underpinnings of aggressive behavior, and one of the candidate genes codes for the catechol-O-methyltransferase (COMT). COMT is involved in catabolizing catecholamines such as dopamine. These neurotransmitters appear to be involved in regulating mood which can contribute to aggression. The most common gene variant studied in the COMT gene is the Valine (Val) to Methionine (Met) substitution at codon 158. We will be reviewing the current literature on this gene variant in aggressive behavior.

Transcriptome analysis of genes and gene networks involved in aggressive behavior in mouse and zebrafish

Despite moderate heritability estimates, the molecular architecture of aggressive behavior remains poorly characterized. This study compared gene expression profiles from a genetic mouse model of aggression with zebrafish, an animal model traditionally used to study aggression. A meta-analytic, cross-species approach was used to identify genomic variants associated with aggressive behavior. The Rankprod algorithm was used to evaluated mRNA differences from prefrontal cortex tissues of three sets of mouse lines (N = 18) selectively bred for low and high aggressive behavior (SAL/LAL, TA/TNA, and NC900/NC100). The same approach was used to evaluate mRNA differences in zebrafish (N = 12) exposed to aggressive or non-aggressive social encounters. Results were compared to uncover genes consistently implicated in aggression across both studies. Seventy-six genes were differentially expressed (PFP < 0.05) in aggressive compared to non-aggressive mice. Seventy genes were differentially expressed in zebrafish exposed to a fight encounter compared to isolated zebrafish. Seven genes (Fos, Dusp1, Hdac4, Ier2, Bdnf, Btg2, and Nr4a1) were differentially expressed across both species 5 of which belonging to a gene-network centred on the c-Fos gene hub. Network analysis revealed an association with the MAPK signaling cascade. In human studies HDAC4 haploinsufficiency is a key genetic mechanism associated with brachydactyly mental retardation syndrome (BDMR), which is associated with aggressive behaviors. Moreover, the HDAC4 receptor is a drug target for valproic acid, which is being employed as an effective pharmacological treatment for aggressive behavior in geriatric, psychiatric, and brain-injury patients. © 2016 Wiley Periodicals, Inc.

A Pilot Study of Psychological Traits in the Sasang Constitution According to the Braverman Nature Assessment

Objectives:

The purpose of this study was to investigate the psychological characteristics of the Sasang constitutions by using Braverman nature assessment (BNA).

Methods:

One hundred seventy-four students participated in this study, and among them, the 142 individuals who had clearly identified Sasang constitutional types were used for the analysis. Sasang constitutions and the Braverman temperaments of the subjects were determined by using a questionnaire for the Sasang constitution classification (QSCC) II and BNA, respectively. Body mass index (BMI) was used to compare the inclinations of the Sasang constitutions and Braverman temperament types.

Results:

Significant differences in Braverman temperament type existed among the Sasang constitutions (P = 0.042), and the relations between Soyangin and the dopamine type and between Taeeumin and the gamma-aminobutyric acid (GABA) type were meaningful. Significant differences were also shown in the comparison with the Yin and the Yang constitutions (P = 0.017), and the post-hoc analysis showed a strong and significant relation between the Yang constitution and the dopamine type and between the Yin constitution and the GABA type. The one–way analysis of variance (ANOVA) and the independent t-test were conducted to examine the BMI and the degree of obesity among the Sasang constitutions and the Braverman temperament types. Concerning the BMI, Taeeumin showed a bigger BMI than the other constitutions (P < 0.001), but no significant differences in the BMI were observed between the Braverman temperament types.

Conclusion:

Soyangin has a close relationship to the dopamine type and Taeeumin has a close relationship to the GABA type. The correlation between two types were more clear when the Yin and the Yang types were compared to Braverman temperaments. These results may serve as a basis for identifying the psychological traits of Sasang constitutional types, especially in regard to the characteristics related to the four Braverman temperament types.

Neural Correlates and Connectivity Underlying Stress-Related Impulse Control Difficulties in Alcoholism

BACKGROUND

Stress triggers impulsive and addictive behaviors, and alcoholism has been frequently associated with increased stress sensitivity and impulse control problems. However, neural correlates underlying the link between alcoholism and impulsivity in the context of stress in patients with alcohol use disorders (AUD) have not been well studied.

METHODS

This study investigated neural correlates and connectivity patterns associated with impulse control difficulties in abstinent AUD patients. Using functional magnetic resonance imaging, brain responses of 37 AUD inpatients, and 37 demographically matched healthy controls were examined during brief individualized imagery trials of stress, alcohol cue, and neutral-relaxing conditions. Stress-related impulsivity was measured using a subscale score of impulse control problems from Difficulties in Emotion Regulation Scale.

RESULTS

Impulse control difficulties in AUD patients were significantly associated with hypo-active response to stress in the ventromedial prefrontal cortex (VmPFC), right caudate, and left lateral PFC (LPFC) compared to the neutral condition (p < 0.01, whole-brain corrected). These regions were used as seed regions to further examine the connectivity patterns with other brain regions. With the VmPFC seed, AUD patients showed reduced connectivity with the anterior cingulate cortex compared to controls, which are core regions of emotion regulation, suggesting AUD patients' decreased ability to modulate emotional response under distressed state. With the right caudate seed, patients showed increased connectivity with the right motor cortex, suggesting increased tendency toward habitually driven behaviors. With the left LPFC seed, decreased connectivity with the dorsomedial PFC (DmPFC), but increased connectivity with sensory and motor cortices were found in AUD patients compared to controls (p < 0.05, whole-brain corrected). Reduced connectivity between the left LPFC and DmPFC was further associated with increased stress-induced anxiety in AUD patients (p < 0.05, with adjusted Bonferroni correction).

CONCLUSIONS

Hypo-active response to stress and altered connectivity in key emotion regulatory regions may account for greater stress-related impulse control problems in alcoholism.

Genome-wide association study of aggressive behaviour in chicken

In the poultry industry, aggressive behaviour is a large animal welfare issue all over the world. To date, little is known about the underlying genetics of the aggressive behaviour. Here, we performed a genome-wide association study (GWAS) to explore the genetic mechanism associated with aggressive behaviour in chickens. The GWAS results showed that a total of 33 SNPs were associated with aggressive behaviour traits (P < 4.6E-6). rs312463697 on chromosome 4 was significantly associated with aggression (P = 2.10905E-07), and it was in the intron region of the sortilin-related VPS10 domain containing receptor 2 (SORCS2) gene. In addition, biological function analysis of the nearest 26 genes around the significant SNPs was performed with Ingenuity Pathway Analysis. An interaction network contained 17 genes was obtained and SORCS2 was involved in this network, interacted with nerve growth factor (NGF), nerve growth factor receptor (NGFR), dopa decarboxylase (L-dopa) and dopamine. After knockdown of SORCS2, the mRNA levels of NGF, L-dopa and dopamine receptor genes DRD1, DRD2, DRD3 and DRD4 were significantly decreased (P < 0.05). In summary, our data indicated that SORCS2 might play an important role in chicken aggressive behaviour through the regulation of dopaminergic pathways and NGF.

Discovery of biochemical biomarkers for aggression: A role for metabolomics in psychiatry

Human aggression encompasses a wide range of behaviors and is related to many psychiatric disorders. We introduce the different classification systems of aggression and related disorders as a basis for discussing biochemical biomarkers and then present an overview of studies in humans (published between 1990 and 2015) that reported statistically significant associations of biochemical biomarkers with aggression, DSM-IV disorders involving aggression, and their subtypes. The markers are of different types, including inflammation markers, neurotransmitters, lipoproteins, and hormones from various classes. Most studies focused on only a limited portfolio of biomarkers, frequently a specific class only. When integrating the data, it is clear that compounds from several biological pathways have been found to be associated with aggressive behavior, indicating complexity and the need for a broad approach. In the second part of the paper, using examples from the aggression literature and psychiatric metabolomics studies, we argue that a better understanding of aggression would benefit from a more holistic approach such as provided by metabolomics. © 2016 Wiley Periodicals, Inc.

The neurobiological basis of human aggression: A review on genetic and epigenetic mechanisms

Aggression is an evolutionary conserved behavior present in most species including humans. Inadequate aggression can lead to long-term detrimental personal and societal effects. Here, we differentiate between proactive and reactive forms of aggression and review the genetic determinants of it. Heritability estimates of aggression in general vary between studies due to differing assessment instruments for aggressive behavior (AB) as well as age and gender of study participants. In addition, especially non-shared environmental factors shape AB. Current hypotheses suggest that environmental effects such as early life stress or chronic psychosocial risk factors (e.g., maltreatment) and variation in genes related to neuroendocrine, dopaminergic as well as serotonergic systems increase the risk to develop AB. In this review, we summarize the current knowledge of the genetics of human aggression based on twin studies, genetic association studies, animal models, and epigenetic analyses with the aim to differentiate between mechanisms associated with proactive or reactive aggression. We hypothesize that from a genetic perspective, the aminergic systems are likely to regulate both reactive and proactive aggression, whereas the endocrine pathways seem to be more involved in regulation of reactive aggression through modulation of impulsivity. Epigenetic studies on aggression have associated non-genetic risk factors with modifications of the stress response and the immune system. Finally, we point to the urgent need for further genome-wide analyses and the integration of genetic and epigenetic information to understand individual differences in reactive and proactive AB. © 2015 Wiley Periodicals, Inc.

Child maltreatment, impulsivity, and antisocial behavior in African American children: Moderation effects from a cumulative dopaminergic gene index

A model examining the effects of an increasing number of maltreatment subtypes experienced on antisocial behavior, as mediated by impulsivity and moderated by a polygenic index of dopaminergic genotypes, was investigated. An African American sample of children (N = 1,012, M age = 10.07) with and without maltreatment histories participated. Indicators of aggression, delinquency, and disruptive peer behavior were obtained from peer- and counselor-rated measures to form a latent variable of antisocial behavior; impulsivity was assessed by counselor report. Five genotypes in four dopaminergic genes (dopamine receptors D4, D2, known as DRD4, DRD2; dopamine active transporter 1, known as DAT1; and catechol-O-methyltransferase, known as COMT) conferring heightened environmental sensitivity were combined into one polygenic index. Using structural equation modeling, a first-stage, moderated-mediation model was evaluated. Age and sex were entered as covariates, both as main effects and in interaction with maltreatment and the gene index. The model had excellent fit: χ2 (32, N = 1,012) = 86.51, p < .001; comparative fit index = 0.982, Tucker-Lewis index = 0.977, root mean square error of approximation = 0.041, and standardized root mean square residual = 0.022. The effect of maltreatment subtypes on antisocial behavior was partially mediated by impulsivity (β = 0.173, p < .001), and these relations were moderated by the number of differentiating dopaminergic genotypes. Specifically, a significant Gene × Environment interaction (β = 0.016, p = .013) indicated that the relation between maltreatment and impulsivity was stronger as children evinced more differentiating genotypes, thereby strengthening the mediational effect of impulsivity on antisocial behavior. These findings elucidate the manner by which maltreated children develop early signs of antisocial behavior, and the genetic mechanisms involved in greater vulnerability for maladaptation in impulse control within the context of child maltreatment.

Repeated, Intermittent Social Defeat across the Entire Juvenile Period Resulted in Behavioral, Physiological, Hormonal, Immunological, and Neurochemical Alterations in Young Adult Male Golden Hamsters

The developing brain is vulnerable to social defeat during the juvenile period. As complements of human studies, animal models of social defeat provide a straightforward approach to investigating the functional and neurobiological consequences of social defeats. Taking advantage of agonist behavior and social defeat in male golden hamster, a set of 6 experiments was conducted to investigate the consequences at multiple levels in young adulthood resulting from repeated, intermittent social defeats or “social threats” across the entire juvenile period. Male hamsters at postnatal day 28 (P28) were randomly assigned to either the social defeat, “social threat”, or arena control group, and they correspondingly received a series of nine social interaction trials (i.e., either social defeat, “social threat”, or arena control conditions) from P33 to P66. At the behavioral level (Experiment 1), we found that repeated social defeats (but not “social threats”) significantly impacted locomotor activity in the familiar context and social interaction in the familiar/unfamiliar social contexts. At the physiological and hormonal levels (Experiments 2 and 3), repeated social defeat significantly enhanced the cortisol and norepinephrine concentrations in blood. Enlargement of the spleen was also found in the social defeat and “social threat” groups. At the immunological level (Experiment 4), the social defeat group showed lower levels of pro-inflammatory cytokines in the hypothalamus and hippocampus but higher concentration of IL-6 in the striatum compared to the other two groups. At the neurochemical level (Experiment 5), the socially defeated hamsters mainly displayed reductions of dopamine, dopamine metabolites, and 5-HT levels in the striatum and decreased level of 5-HT in the hippocampus. In Experiment 6, an increase in the spine density of hippocampal CA1 pyramidal neurons was specifically observed in the “social threat” group. Collectively, our findings indicate that repeated, intermittent social defeats throughout entire adolescence in hamsters impact their adult responses at multiple levels. Our results also suggest that the “social threat” group may serve as an appropriate control. This study further suggest that the alterations of behavioral responses and neurobiological functions in the body and brain might provide potential markers to measure the negative consequences of chronic social defeats.

COMT and ANKK1 Genetics Interact With Depression to Influence Behavior Following Severe TBI: An Initial Assessment

OBJECTIVE

Genetic variations in the dopamine (DA) system are associated with cortical-striatal behavior in multiple populations. This study assessed associations of functional polymorphisms in the ankyrin repeat and kinase domain (ANKK1; Taq1a) and catechol-O-methyltransferase (COMT; Val158Met) genes with behavioral dysfunction following traumatic brain injury (TBI).

PARTICIPANTS

This was a prospective study of 90 survivors of severe TBI recruited from a level 1 trauma center.

MAIN MEASURES

The Frontal Systems Behavior Scale, a self- or family report questionnaire evaluating behavior associated with frontal lobe dysfunction, was completed 6 and 12 months postinjury. Depression was measured concurrently with the Patient Health Questionnaire-9. Study participants were genotyped for Val158Met and Taq1a polymorphisms.

RESULTS

No statistically significant behavioral differences were observed by Taq1a or Val158Met genotype alone. At 12 months, among those with depression, Met homozygotes (Val158Met) self-reported worse behavior than Val carriers (P = .015), and A2 homozygotes (Taq1a) self-reported worse behavior than A1 carriers (P = .028) in bivariable analysis. Multivariable models suggest an interaction between depression and genetic variation with behavior at 12 months post-TBI, and descriptive analysis suggests that carriage of both risk alleles may contribute to worse behavioral performance than carriage of either risk allele alone.

CONCLUSION

In the context of depression, Val158Met and Taq1a polymorphisms are individually associated with behavioral dysfunction 12 months following severe TBI, with preliminary evidence suggesting cumulative, or perhaps epistatic, effects of COMT and ANKK1 on behavioral dysfunction.

Early antipsychotic treatment in childhood/adolescent period has long-term effects on depressive-like, anxiety-like and locomotor behaviours in adult rats

Childhood/adolescent antipsychotic drug (APD) use is exponentially increasing worldwide, despite limited knowledge of the long-term effects of early APD treatment. Whilst investigations have found that early treatment has resulted in some alterations to dopamine and serotonin neurotransmission systems (essential to APD efficacy), there have only been limited studies into potential long-term behavioural changes. This study, using an animal model for childhood/adolescent APD treatment, investigated the long-term effects of aripiprazole, olanzapine and risperidone on adult behaviours of male and female rats. Open-field/holeboard, elevated plus maze (EPM), social interaction and forced swim (FS) tests were then conducted in adult rats. Our results indicated that in the male cohort, early risperidone and olanzapine treatment elicited long-term hyper-locomotor effects (open-field/holeboard and FS tests), whilst a decrease in depressive-like behaviour (in FS test) was observed in response to olanzapine treatment. Furthermore, anxiolytic-like behaviours were found following testing in the open-field/holeboard and EPM in response to all three drug treatments. Effects in the female cohort, however, were to a far lesser extent, with behavioural attributes indicative of an increased depressive-like behaviour and hypo-locomotor activity exhibited in the FS test following early risperidone and olanzapine treatment. These results suggest that various APDs have different long-term effects on the behaviours of adult rats.

Neural Basis of Brain Dysfunction Produced by Early Sleep Problems

There is a wealth of evidence that disrupted sleep and circadian rhythms, which are common in modern society even during the early stages of life, have unfavorable effects on brain function. Altered brain function can cause problem behaviors later in life, such as truancy from or dropping out of school, quitting employment, and committing suicide. In this review, we discuss findings from several large cohort studies together with recent results of a cohort study using the marshmallow test, which was first introduced in the 1960s. This test assessed the ability of four-year-olds to delay gratification and showed how this ability correlated with success later in life. The role of the serotonergic system in sleep and how this role changes with age are also discussed. The serotonergic system is involved in reward processing and interactions with the dorsal striatum, ventral striatum, and the prefrontal cortex are thought to comprise the neural basis for behavioral patterns that are affected by the quantity, quality, and timing of sleep early in life.

Identified Serotonin-Releasing Neurons Induce Behavioral Quiescence and Suppress Mating in Drosophila

Animals show different levels of activity that are reflected in sensory responsiveness and endogenously generated behaviors. Biogenic amines have been determined to be causal factors for these states of arousal. It is well established that, in Drosophila, dopamine and octopamine promote increased arousal. However, little is known about factors that regulate arousal negatively and induce states of quiescence. Moreover, it remains unclear whether global, diffuse modulatory systems comprehensively affecting brain activity determine general states of arousal. Alternatively, individual aminergic neurons might selectively modulate the animals' activity in a distinct behavioral context. Here, we show that artificially activating large populations of serotonin-releasing neurons induces behavioral quiescence and inhibits feeding and mating. We systematically narrowed down a role of serotonin in inhibiting endogenously generated locomotor activity to neurons located in the posterior medial protocerebrum. We identified neurons of this cell cluster that suppress mating, but not feeding behavior. These results suggest that serotonin does not uniformly act as global, negative modulator of general arousal. Rather, distinct serotoninergic neurons can act as inhibitory modulators of specific behaviors.

SIGNIFICANCE STATEMENT

An animal's responsiveness to external stimuli and its various types of endogenously generated, motivated behavior are highly dynamic and change between states of high activity and states of low activity. It remains unclear whether these states are mediated by unitary modulatory systems globally affecting brain activity, or whether distinct neurons modulate specific neuronal circuits underlying particular types of behavior. Using the model organism Drosophila melanogaster, we find that activating large proportions of serotonin-releasing neurons induces behavioral quiescence. Moreover, distinct serotonin-releasing neurons that we genetically isolated and identified negatively affect aspects of mating behavior, but not food uptake. This demonstrates that individual serotoninergic neurons can modulate distinct types of behavior selectively.

Looking for reward in all the wrong places: dopamine receptor gene polymorphisms indirectly affect aggression through sensation-seeking

Individuals with genotypes that code for reduced dopaminergic brain activity often exhibit a predisposition toward aggression. However, it remains largely unknown how dopaminergic genotypes may increase aggression. Lower-functioning dopamine systems motivate individuals to seek reward from external sources such as illicit drugs and other risky experiences. Based on emerging evidence that aggression is a rewarding experience, we predicted that the effect of lower-functioning dopaminergic functioning on aggression would be mediated by tendencies to seek the environment for rewards. Caucasian female and male undergraduates (N = 277) were genotyped for five polymorphisms of the dopamine D2 receptor (DRD2) gene; they reported their previous history of aggression and their dispositional reward-seeking. Lower-functioning DRD2 profiles were associated with greater sensation-seeking, which then predicted greater aggression. Our findings suggest that lower-functioning dopaminergic activity puts individuals at risk for violence because it motivates them to experience aggression's hedonically rewarding qualities.

Neural and Behavioral Correlates of Alcohol-Induced Aggression Under Provocation

Although alcohol consumption is linked to increased aggression, its neural correlates have not directly been studied in humans so far. Based on a comprehensive neurobiological model of alcohol-induced aggression, we hypothesized that alcohol-induced aggression would go along with increased amygdala and ventral striatum reactivity and impaired functioning of the prefrontal cortex (PFC) under alcohol. We measured neural and behavioral correlates of alcohol-induced aggression in a provoking vs non-provoking condition with a variant of the Taylor aggression paradigm (TAP) allowing to differentiate between reactive (provoked) and proactive (unprovoked) aggression. In a placebo-controlled cross-over design with moderate alcohol intoxication (~0.6 g/kg), 35 young healthy adults performed the TAP during functional magnetic resonance imaging (fMRI). Analyses revealed that provoking vs non-provoking conditions and alcohol vs placebo increased aggression and decreased brain responses in the anterior cingulate cortex/dorso-medial PFC (provoking<non-provoking) and the ventral striatum (alcohol<placebo) across our healthy sample. Interestingly, alcohol specifically increased proactive (unprovoked) but not reactive (provoked) aggression (alcohol × provocation interaction). However, investigation of inter-individual differences revealed (1) that pronounced alcohol-induced proactive aggression was linked to higher levels of aggression under placebo, and (2) that pronounced alcohol-induced reactive aggression was related to increased amygdala and ventral striatum reactivity under alcohol, providing evidence for their role in human alcohol-induced reactive aggression. Our findings suggest that in healthy young adults a liability for alcohol-induced aggression in a non-provoking context might depend on overall high levels of aggression, but on alcohol-induced increased striatal and amygdala reactivity when triggered by provocation.

Mesocorticolimbic dopamine functioning in primary psychopathy: A source of within-group heterogeneity

Despite similar emotional deficiencies, primary psychopathic individuals can be situated on a continuum that spans from controlled to disinhibited. The constructs on which primary psychopaths are found to diverge, such as self-control, cognitive flexibility, and executive functioning, are crucially regulated by dopamine (DA). As such, the goal of this review is to examine which specific alterations in the meso-cortico-limbic DA system and corresponding genes (e.g., TH, DAT, COMT, DRD2, DRD4) might bias development towards a more controlled or disinhibited expression of primary psychopathy. Based on empirical data, it is argued that primary psychopathy is generally related to a higher tonic and population activity of striatal DA neurons and lower levels of D2-type DA receptors in meso-cortico-limbic projections, which may boost motivational drive towards incentive-laden goals, dampen punishment sensitivity, and increase future reward-expectancy. However, increasingly higher levels of DA activity in the striatum (moderate versus pathological elevations), lower levels of DA functionality in the prefrontal cortex, and higher D1-to-D2-type receptor ratios in meso-cortico-limbic projections may lead to increasingly disinhibited and impetuous phenotypes of primary psychopathy. Finally, in order to provide a more coherent view on etiological mechanisms, we discuss interactions between DA and serotonin that are relevant for primary psychopathy.

Dual regulating effect of Ningdong granule on extracellular dopamine content of two kinds of Tourette's syndrome rat models

Tourette's syndrome (TS) is an inherited chronic neuropsychiatric disorder characterized by involuntary stereotyped motor and phonic behaviors called tics. Its pathogenesis is still unclear and its treatment remains limited. Our previous basic and clinical studies have shown that traditional Chinese medicine (TCM) preparation Ningdong granule (NDG) is effective for the treatment of TS with little side effects. In the current study, two TS rat models (Apomorphine (Apo)- and 3,3'-iminodipropionitrile (IDPN)-induced) were used to explore the dual regulating effects and mechanisms of NDG on extracellular DA concentration. We found that NDG could regulate the extracellular DA concentration dually: it could make a gradual recovery in extracellular DA content from both an up-regulated level in Apo-induced rats and down-regulated level in IDPN-induced rats measured by high-performance liquid chromatography (HPLC). The protein expression of DA transporter (DAT) was measured by Western blot and the result showed that NDG could elevate DAT expression when DA release was up-regulated and could decrease DAT expression when extracellular DA concentration was down-regulated. The main mechanism of the dual regulating effect of NDG on extracellular DA release might be related to DAT protein expression in TS, through which the released DA is re-uptaken into nerve terminals. Taken together, compared with conventional single-target anti-tics drugs such as haloperidol (Hal), NDG with the dual regulating effect would be more significant for TS treatment.

Cocaine self-administration in Wistar-Kyoto rats: a behavioral and biochemical analysis

Depression and cocaine abuse disorders are common concurrent diagnoses. In the present study, we employed Wistar-Kyoto (WKY) rats that showed a depressive-like phenotype to study intravenous cocaine self-administration and extinction/reinstatement procedures. We also investigated the basal tissue level of neurotransmitters, their metabolites and plasma corticosterone (CORT) concentrations in WKY rats, bulbectomized (OBX) rats, and control rats. The WKY rats exhibited an attenuation of the cocaine-associated lever presses and cocaine intake during the acquisition/maintenance of cocaine self-administration only under specific conditions. Active lever presses exhibited by the WKY rats and control animals did not differ during the extinction training and cocaine-seeking behaviors. The WKY rats demonstrated alterations in the basal levels of dopamine, norepinephrine, and serotonin in selected brain structures involved in depression and drug addiction. The changes in the level of neurotransmitters in these animals refer not only to the control (Wistar) rats but also to bulbectomized animals, which represent another depression model. Furthermore, we identified unchanged levels of CORT in the WKY and OBX rats during the light phase and free-stress conditions. This finding suggests that WKY rats should not be used to investigate the co-occurrence of depression and cocaine addiction, as this rat strain does not show an enhanced risk of relapse.

Serum neuron-specific enolase, biogenic amino-acids and neurobehavioral function in lead-exposed workers from lead-acid battery manufacturing process

Background:

The interaction between serum neuron-specific enolase (NSE), biogenic amino-acids and neurobehavioral function with blood lead levels in workers exposed to lead form lead-acid battery manufacturing process was not studied.

Objective:

To evaluate serum NSE and biogenic amino-acids (dopamine and serotonin) levels, and neurobehavioral performance among workers exposed to lead from lead-acid storage battery plant, and its relation with blood lead levels (BLLs).

Methods:

In a cross-sectional study, we performed biochemical and neurobehavioral function tests on 146 workers exposed to lead from lead-acid battery manufacturing process. BLLs were assessed by an atomic absorption spectrophotometer. Serum NSE, dopamine and serotonin were measured by ELISA. Neurobehavioral functions were assessed by CDC-recommended tests—simple reaction time (SRT), symbol digit substitution test (SDST), and serial digit learning test (SDLT).

Results:

There was a significant correlation (r 0.199, p<0.05) between SDST and BLL. SDLT and SRT had also a significant positive correlation (r 0.238, p<0.01). NSE had a negative correlation (r –0.194, p<0.05) with serotonin level. Multiple linear regression analysis revealed that both SRT and SDST had positive significant associations with BLL. SRT also had a positive significant association with age.

Conclusion:

Serum NSE cannot be used as a marker for BLL. The only domain of neurobehavioral function tests that is affected by increased BLL in workers of lead-acid battery manufacturing process is that of the "attention and perception" (SDST).

Dissociable Effects of Serotonin and Dopamine on the Valuation of Harm in Moral Decision Making

An aversion to harming others is a core component of human morality and is disturbed in antisocial behavior. Deficient harm aversion may underlie instrumental and reactive aggression, which both feature in psychopathy. Past work has highlighted monoaminergic influences on aggression, but a mechanistic account of how monoamines regulate antisocial motives remains elusive. We previously observed that most people show a greater aversion to inflicting pain on others than themselves. Here, we investigated whether this hyperaltruistic disposition is susceptible to monoaminergic control. We observed dissociable effects of the serotonin reuptake inhibitor citalopram and the dopamine precursor levodopa on decisions to inflict pain on oneself and others for financial gain. Computational models of choice behavior showed that citalopram increased harm aversion for both self and others, while levodopa reduced hyperaltruism. The effects of citalopram were stronger than those of levodopa. Crucially, neither drug influenced the physical perception of pain or other components of choice such as motor impulsivity or loss aversion, suggesting a direct and specific influence of serotonin and dopamine on the valuation of harm. We also found evidence for dose dependency of these effects. Finally, the drugs had dissociable effects on response times, with citalopram enhancing behavioral inhibition and levodopa reducing slowing related to being responsible for another's fate. These distinct roles of serotonin and dopamine in modulating moral behavior have implications for potential treatments of social dysfunction that is a common feature as well as a risk factor for many psychiatric disorders.

Separate and interactive contributions of weak inhibitory control and threat sensitivity to prediction of suicide risk

Biobehavioral dispositions can serve as valuable referents for biologically oriented research on core processes with relevance to many psychiatric conditions. The present study examined two such dispositional variables-weak response inhibition (or disinhibition; INH-) and threat sensitivity (or fearfulness; THT+)-as predictors of the serious transdiagnostic problem of suicide risk in two samples: male and female outpatients from a U.S. clinic (N=1078), and a population-based male military cohort from Finland (N=3855). INH- and THT+ were operationalized through scores on scale measures of disinhibition and fear/fearlessness, known to be related to DSM-defined clinical conditions and brain biomarkers. Suicide risk was assessed by clinician ratings (clinic sample) and questionnaires (both samples). Across samples and alternative suicide indices, INH- and THT+ each contributed uniquely to prediction of suicide risk-beyond internalizing and externalizing problems in the case of the clinic sample where diagnostic data were available. Further, in both samples, INH- and THT+ interactively predicted suicide risk, with individuals scoring concurrently high on both dispositions exhibiting markedly augmented risk. Findings demonstrate that dispositional constructs of INH- and THT+ are predictive of suicide risk, and hold potential as referents for biological research on suicidal behavior.

Withdrawal from repeated administration of a low dose of reserpine induced opposing adaptive changes in the noradrenaline and serotonin system function: a behavioral and neurochemical ex vivo and in vivo studies in the rat

Reserpine is an inhibitor of the vesicular monoamine transporter 2 (VMAT2) and monoamine releaser, so it can be used as a pharmacological model of depression. In the present paper, we investigated the behavioral and neurochemical effects of withdrawal from acute and repeated administration of a low dose of reserpine (0.2 mg/kg) in Wistar Han rats. We demonstrated the behavioral and receptor oversensitivity (postsynaptic dopamine D1) during withdrawal from chronic reserpine. It was accompanied by a significant increase in motility in the locomotor activity test and climbing behavior in the forced swim test (FST). Neurochemical studies revealed that repeated but not acute administration the a low dose of reserpine triggered opposing adaptive changes in the noradrenergic and serotonin system function analyzed during reserpine withdrawal, i.e. 48 h after the last injection. The tissue concentration of noradrenaline was significantly decreased in the hypothalamus and nucleus accumbens only after repeated drug administration (by about 20% and 35% vs. control; p<0.05, respectively). On the other hand, the concentration of its extraneuronal metabolite, normetanephrine (NM) increased significantly in the VTA during withdrawal both from acute and chronic reserpine. The serotonin concentration was significantly reduced in the VTA after chronic reserpine (by about 40% vs. the control group, p<0.05) as well as its main metabolite, 5-HIAA (by about 30% vs. control; p<0.05) in the VTA and hypothalamus. Dopamine and its metabolites were not changed after acute or chronic reserpine administration. In vivo microdialysis studies clearly evidenced the lack of the effect of a single dose of reserpine, and its distinct effects after chronic treatment on the release of noradrenaline and serotonin in the rat striatum. In fact, the withdrawal from repeated administration of reserpine significantly increased an extraneuronal concentration of noradrenaline in the rat striatum but at the same time produced a distinct fall in the extraneuronal serotonin in this brain structure. On the basis of the presented behavioral and neurochemical experiments, we suggest that chronic administration of reserpine even in such low dose which not yet acted on the release of monoamines but produced an inhibition of VMAT2 caused a long-lasting disadvantageous effect of plasticity in the brain resembling depressive disorders.

Impulsive aggression, delay discounting, and adolescent suicide attempts: effects of current psychotropic medication use and family history of suicidal behavior

OBJECTIVE

Impulsive-aggressive behaviors have been consistently implicated in the phenomenology, neurobiology, and familial aggregation of suicidal behavior. The purpose of this study was to extend previous work by examining laboratory behavioral measures of delayed reward impulsivity and impulsive aggression in adolescent suicide attempters and never-suicidal comparison subjects.

METHODS

Using the Point Subtraction Aggression Paradigm (PSAP) and the Delay Discounting Task (DDQ), the authors examined delay discounting and impulsive aggression in 40 adolescent suicide attempters, ages 13-18, and 40 never-suicidal, demographically matched psychiatric comparison subjects.

RESULTS

Overall, suicide attempters and comparison subjects performed similarly on the PSAP and DDQ. There was a significant group by current psychotropic medication use interaction (p=0.013) for mean aggressive responses on the PSAP. Group comparisons revealed that attempters emitted more aggressive responses per provocation than comparison subjects, only in those not on psychotropic medication (p=0.049), whereas for those currently treated with psychotropic medication, there were no group differences (p>0.05). This interaction effect was specific to current antidepressant use. Among all subjects, family history of suicidal behavior (suicide or suicide attempt) in first degree relatives was significantly correlated with both delay discounting (r=-0.22, p=0.049), and aggressive responding (r=0.27, p=0.015). Family history of suicidal behavior was associated with delay discounting, but not with aggressive responding on the PSAP, after controlling for relevant covariates.

CONCLUSIONS

In this study, impulsive-aggressive responding was associated with suicide attempt only in those not being treated with antidepressants. Future work to replicate and extend these findings could have important therapeutic implications for the treatment of depressed suicide attempters, many of whom are affected by impulsive aggression.