Effects of response requirement and alcohol on human aggressive responding

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.

GABAA Receptor-Modulating Steroids in Relation to Women's Behavioral Health

In certain women, increased negative mood relates to the progesterone metabolite, allopregnanolone (allo), during the luteal phase of ovulatory menstrual cycles, the premenstrual dysphoric disorder (PMDD). In anovulatory cycles, no symptom or sex steroid increase occurs but symptoms return during progesterone/allo treatment. Allo is a potent GABAA receptor-modulating steroid and as such is expected to be calming and anxiolytic. A relation to negative mood is unexpected. However, this paradoxical effect can be induced by all GABAA receptor modulators in low concentrations whereas higher concentrations are calming. The severity of the mood symptoms relate to allo in an inverted U-shaped curve at endogenous luteal-phase serum concentrations. Allo's effects on the GABAA receptor can be antagonized by isoallopregnanolone (ISO), an antagonist to allo. ISO has also been used in a preliminary clinical trial on PMDD ameliorating symptoms with good effect in PMDD patients.

Impulsive-Aggressive Traits, Serotonin Function, and Alcohol-Enhanced Aggression

Although alcohol consumption is involved in most acts of violence, most people do not become violent when they drink. Individuals also respond differently to alcohol on laboratory measures of aggression. The objective of this study was to determine whether individual differences in the effects of alcohol on a laboratory measure of aggression are related to specific personality traits and/or serotonin function, as measured by prolactin response to pharmacochallenge. Psychometric scales for impulsiveness, aggression, and anger, as well as a probe for suspiciousness, were administered to 10 healthy male social drinkers. Trait serotonin function was determined by citalopram challenge. The effect of alcohol on the Point Subtraction Aggression Paradigm was determined by comparing aggression scores with and without 1 g/kg alcohol. Impulsivity scores were significantly correlated with the change in aggressive responding after alcohol. Aggression, anger, and suspiciousness scores were not. Prolactin response did not predict the effect of alcohol on aggressive responding. The results suggest that trait impulsiveness may mediate the effects of alcohol on aggression in normal males.

Chronic tiagabine administration and aggressive responding in individuals with a history of substance abuse and antisocial behavior

Anticonvulsants, notably those which modulate GABA activity, have shown efficacy in reducing aggressive behavior. Previously, we found dose-related decreases in human aggressive responding following acute tiagabine administration. Here, we examined the effects of chronic tiagabine over a 5-week period. Twelve individuals at increased risk for aggressive and violent behavior (currently on parole/probation with personality and/or substance use disorders) were randomly assigned to placebo (n = 6) or an escalating dose sequence of placebo, 4 mg, 8 mg, 12 mg, placebo (n = 6). Data were analyzed using both frequentist and Bayesian mixed models, evaluating aggressive behavior as a function of time, dose condition, and their interaction. For aggressive responding, there was a significant interaction of drug condition and time. Aggression in the tiagabine condition decreased for each additional week in the study, while participants in the placebo condition failed to demonstrate similar change over time. For monetary-reinforced responding, no drug or drug by time interactions were observed, suggesting specificity of drug effects on aggression. The small number of subjects limits the generality of the findings, and previous studies with tiagabine are limited to acute dosing and case report investigations. However, the present data provide an indication that tiagabine merits further examination as an agent for management of impulsive aggression.

Paradoxical effects of GABA-A modulators may explain sex steroid induced negative mood symptoms in some persons

Some women have negative mood symptoms, caused by progestagens in hormonal contraceptives or sequential hormone therapy or by progesterone in the luteal phase of the menstrual cycle, which may be attributed to metabolites acting on the GABA-A receptor. The GABA system is the major inhibitory system in the adult CNS and most positive modulators of the GABA-A receptor (benzodiazepines, barbiturates, alcohol, GABA steroids), induce inhibitory (e.g. anesthetic, sedative, anticonvulsant, anxiolytic) effects. However, some individuals have adverse effects (seizures, increased pain, anxiety, irritability, aggression) upon exposure. Positive GABA-A receptor modulators induce strong paradoxical effects including negative mood in 3%-8% of those exposed, while up to 25% have moderate symptoms. The effect is biphasic: low concentrations induce an adverse anxiogenic effect while higher concentrations decrease this effect and show inhibitory, calming properties. The prevalence of premenstrual dysphoric disorder (PMDD) is also 3%-8% among women in fertile ages, and up to 25% have more moderate symptoms of premenstrual syndrome (PMS). Patients with PMDD have severe luteal phase-related symptoms and show changes in GABA-A receptor sensitivity and GABA concentrations. Findings suggest that negative mood symptoms in women with PMDD are caused by the paradoxical effect of allopregnanolone mediated via the GABA-A receptor, which may be explained by one or more of three hypotheses regarding the paradoxical effect of GABA steroids on behavior: (1) under certain conditions, such as puberty, the relative fraction of certain GABA-A receptor subtypes may be altered, and at those subtypes the GABA steroids may act as negative modulators in contrast to their usual role as positive modulators; (2) in certain brain areas of vulnerable women the transmembrane Cl(-) gradient may be altered by factors such as estrogens that favor excitability; (3) inhibition of inhibitory neurons may promote disinhibition, and hence excitability. This article is part of a Special Issue entitled: Neuroactive Steroids: Focus on Human Brain.

Neurosteroids and GABA-A Receptor Function

Neurosteroids represent a class of endogenous steroids that are synthesized in the brain, the adrenals, and the gonads and have potent and selective effects on the GABAA-receptor. 3α-hydroxy A-ring reduced metabolites of progesterone, deoxycorticosterone, and testosterone are positive modulators of GABA(A)-receptor in a non-genomic manner. Allopregnanolone (3α-OH-5α-pregnan-20-one), 5α-androstane-3α, 17α-diol (Adiol), and 3α5α-tetrahydrodeoxycorticosterone (3α5α-THDOC) enhance the GABA-mediated Cl(-) currents acting on a site (or sites) distinct from the GABA, benzodiazepine, barbiturate, and picrotoxin binding sites. 3α5α-P and 3α5α-THDOC potentiate synaptic GABA(A)-receptor function and activate δ-subunit containing extrasynaptic receptors that mediate tonic currents. On the contrary, 3β-OH pregnane steroids and pregnenolone sulfate (PS) are GABA(A)-receptor antagonists and induce activation-dependent inhibition of the receptor. The activities of neurosteroid are dependent on brain regions and types of neurons. In addition to the slow genomic action of the parent steroids, the non-genomic, and rapid actions of neurosteroids play a significant role in the GABA(A)-receptor function and shift in mood and memory function. This review describes molecular mechanisms underlying neurosteroid action on the GABA(A)-receptor, mood changes, and cognitive functions.

Alcohol dose and aggression: another reason why drinking more is a bad idea

OBJECTIVE

Numerous studies have examined the impact of alcohol on violence; however, only a small number have addressed differences elicited by different doses of alcohol. Such studies are limited by mixed findings, small sample sizes, inconsistent alcohol doses and control conditions, a bias toward studying only male participants, and the predominant use of only one particular measure to assess aggression. The present laboratory investigation was designed to elucidate and advance this literature by improving on these limitations.

METHOD

Participants were 187 (95 men and 92 women) social drinkers. Following the consumption of one of six alcohol doses (i.e., 0.0 g/kg, 0.125 g/kg, 0.25 g/kg, 0.5 g/kg, 0.75 g/kg, and 1.0 g/kg), participants were tested on a laboratory task in which electric shocks were received from and administered to a fictitious opponent under the guise of a competitive reaction-time task. Aggression was operationalized as the intensity and duration of shocks administered to one's "opponent."

RESULTS

Analyses revealed a highly significant positive linear trend between alcohol dose and aggression for both genders.

CONCLUSIONS

Our data aid in clarifying a body of literature that has been afflicted with numerous limitations and will help guide the selection of alcohol doses for researchers conducting future laboratory-based aggression studies.

Teens with heavy prenatal cocaine exposure respond to experimental social provocation with escape not aggression

Preclinical data show that, compared to no exposure, prenatal cocaine exposure (PCE) has age-dependent effects on social interaction and aggression. The aim of this clinical study was to determine how heavy/persistent PCE--after controlling for other prenatal drug exposures, sex and postnatal factors--predicts behavioral sensitivity to provocation (i.e., reactive aggression) using a well-validated human laboratory model of aggression. African American teens (mean=14.2 years old) with histories of heavy/persistent PCE (maternal cocaine use ≥ 2 times/week during pregnancy, or positive maternal or infant urine/meconium test at delivery; n=86) or none/some exposure (NON: maternal cocaine use < 2 times/week during pregnancy; n=330) completed the Point Subtraction Aggression Paradigm. In this task, teens competed in a computer game against a fictitious opponent. There were three possible responses: (a) earn points, to exchange for money later; or (b) "aggress" against the fictitious opponent by subtracting their points; or (c) escape temporarily from point subtraction perpetrated by the fictitious opponent. The PCE group responded significantly more frequently on the escape option than the NON group, but did not differ in aggressive or money-earning responses. These data indicate that PCE-teens provoked with a social stressor exhibit a behavioral preference for escape (negative reinforcement) than for aggressive (retaliatory) or appetitive (point- or money-reinforced) responses. These findings are consistent with preclinical data showing that social provocation of adolescent or young adult offspring after PCE is associated with greater escape behavior, inferring greater submission, social withdrawal, or anxiety, as opposed to aggressive behavior.

Sex steroid induced negative mood may be explained by the paradoxical effect mediated by GABAA modulators

Certain women experience negative mood symptoms as a result of progesterone during the luteal phase of the menstrual cycle, progestagens in hormonal contraceptives, or the addition of progesterone or progestagens in sequential hormone therapy (HT). This phenomenon is believed to be mediated via the action of the progesterone metabolites on the GABA(A) system, which is the major inhibitory system in the mammalian CNS. The positive modulators of the GABA(A) receptor include allopregnanolone and pregnanolone, both neuroactive metabolites of progesterone, as well as benzodiazepines, barbiturates, and alcohol. Studies on the effect of GABA(A) receptor modulators have shown contradictory results; although human and animal studies have revealed beneficial properties such as anaesthesia, sedation, anticonvulsant effects, and anxiolytic effects, recent reports have also indicated adverse effects such as anxiety, irritability, and aggression. It has actually been suggested that several GABA(A) receptor modulators, including allopregnanolone, have biphasic effects, in that low concentrations increase an adverse, anxiogenic effect whereas higher concentrations decrease this effect and show beneficial, calming properties. The allopregnanolone increase during the luteal phase in fertile women, as well as during the addition of progesterone in HT, has been shown to induce adverse mood in women. The severity of these mood symptoms is related to the allopregnanolone serum concentrations in a manner similar to an inverted U-shaped curve. Negative mood symptoms occur when the serum concentration of allopregnanolone is similar to endogenous luteal phase levels, while low and high concentrations have less effect on mood. It has also been shown that progesterone/allopregnanolone treatment in women increases the activity in the amygdala (as measured with functional magnetic resonance imaging) in a similar way to the changes seen during anxiety reactions. However, it is evident that only certain women experience adverse mood during progesterone or GABA(A) receptor modulator treatments. Women with premenstrual dysphoric disorder (PMDD) have severe luteal phase related symptoms; in this phase, they show changes in GABA(A) receptor sensitivity and GABA concentrations that are related to the severity of the condition. These findings suggest that negative mood symptoms in women with PMDD are caused by the paradoxical effect of allopregnanolone mediated via the GABA(A) receptor.

CONCLUSION

Progesterone and progestagens induce negative mood, most probably via their GABA(A) receptor active metabolites. In postmenopausal women treated with progesterone and animals treated with allopregnanolone, there is a bimodal association between serum allopregnanolone concentration and adverse mood, resembling an inverted U-shaped curve. In humans, the maximal effective concentration of allopregnanolone for producing negative mood is within the range of physiological luteal phase serum concentrations.

Evaluation of behavioral impulsivity and aggression tasks as endophenotypes for borderline personality disorder

Borderline personality disorder (BPD) is marked by aggression and impulsive, often self-destructive behavior. Despite the severe risks associated with BPD, relatively little is known about the disorder's etiology. Identification of genetic correlates (endophenotypes) of BPD would improve the prospects of targeted interventions for more homogeneous subsets of borderline patients characterized by specific genetic vulnerabilities. The current study evaluated behavioral measures of aggression and impulsivity as potential endophenotypes for BPD. Subjects with BPD (N=127), a non cluster B personality disorder (OPD N=122), or healthy volunteers (HV N=112) completed self report and behavioral measures of aggression, motor impulsivity and cognitive impulsivity. Results showed that BPD subjects demonstrated more aggression and motor impulsivity than HV (but not OPD) subjects on behavioral tasks. In contrast, BPD subjects self-reported more impulsivity and aggression than either comparison group. Subsequent analyses showed that among BPD subjects behavioral aggression was associated with self-reported aggression, while behavioral and self-report impulsivity measures were more modestly associated. Overall, the results provide partial support for the use of behavioral measures of aggression and motor impulsivity as endophenotypes for BPD, with stronger support for behavioral aggression measures as an endophenotype for aggression within BPD samples.

Phenotypic and transcriptional response to selection for alcohol sensitivity in Drosophila melanogaster

Gene-expression profiling combined with selection for genetically divergent Drosophila lines either highly sensitive or resistant to ethanol exposure has been used to identify candidate genes that affect alcohol sensitivity, including 23 novel genes that have human orthologs.

Background

Alcoholism is a complex disorder determined by interactions between genetic and environmental risk factors. Drosophila represents a powerful model system to dissect the genetic architecture of alcohol sensitivity, as large numbers of flies can readily be reared in defined genetic backgrounds and under controlled environmental conditions. Furthermore, flies exposed to ethanol undergo physiological and behavioral changes that resemble human alcohol intoxication, including loss of postural control, sedation, and development of tolerance.

Results

We performed artificial selection for alcohol sensitivity for 35 generations and created duplicate selection lines that are either highly sensitive or resistant to ethanol exposure along with unselected control lines. We used whole genome expression analysis to identify 1,678 probe sets with different expression levels between the divergent lines, pooled across replicates, at a false discovery rate of q < 0.001. We assessed to what extent genes with altered transcriptional regulation might be causally associated with ethanol sensitivity by measuring alcohol sensitivity of 37 co-isogenic P-element insertional mutations in 35 candidate genes, and found that 32 of these mutants differed in sensitivity to ethanol exposure from their co-isogenic controls. Furthermore, 23 of these novel genes have human orthologues.

Conclusion

Combining whole genome expression profiling with selection for genetically divergent lines is an effective approach for identifying candidate genes that affect complex traits, such as alcohol sensitivity. Because of evolutionary conservation of function, it is likely that human orthologues of genes affecting alcohol sensitivity in Drosophila may contribute to alcohol-associated phenotypes in humans.

Allopregnanolone decrease with symptom improvement during placebo and gonadotropin-releasing hormone agonist treatment in women with severe premenstrual syndrome

BACKGROUND

Neurosteroids such as allopregnanolone and pregnanolone are suggested to be of importance for the pathophysiology of premenstrual dysphoric disorder. The aim of this study was to investigate whether the luteal-phase serum concentrations of these neurosteroids are associated with improvement of premenstrual symptoms in 12 women with severe premenstrual syndrome after treatment with low-dose gonadotropin-releasing hormone agonist and placebo.

METHODS

Daily ratings for mood and physical symptoms were made prior to treatment and throughout the study. Serum progesterone, allopregnanolone and pregnanolone were assessed in the luteal phase (cycle day -9 to cycle day -1). Based on their symptom ratings, subjects were grouped as either buserelin responders (n = 6) or placebo responders (n = 6).

RESULTS

Buserelin responders displayed decreased levels of allopregnanolone (p < 0.05) and progesterone (p < 0.05) in parallel with improvement of symptoms. During the placebo treatment, the placebo responders had lower serum allopregnanolone concentrations than buserelin responders (p < 0.05). This was associated with improvement in symptoms compared with pre-treatment ratings.

CONCLUSION

Treatment response, whether induced by buserelin or placebo, appears to be associated with a decrease in allopregnanolone concentration.

Allopregnanolone concentration and mood--a bimodal association in postmenopausal women treated with oral progesterone

RATIONALE

Allopregnanolone effects on mood in postmenopausal women are unclear thus far.

OBJECTIVES

Allopregnanolone is a neuroactive steroid with contradictory effects. Anaesthetic, sedative, and anxiolytic as well as aggressive and anxiogenic properties have been reported. The aim of this study is to compare severity of negative mood between women receiving different serum allopregnanolone concentrations during progesterone treatment.

MATERIALS AND METHODS

A randomized, placebo-controlled, double-blind, crossover study of postmenopausal women (n=43) treated with 2 mg estradiol daily during four treatment cycles. Oral micronized progesterone at 30, 60, and 200 mg/day, and placebo were added sequentially to each cycle. Participants kept daily symptom ratings using a validated rating scale. Blood samples for progesterone and allopregnanolone analyses were collected during each treatment cycle.

RESULTS

During progesterone treatment, women had significantly higher negative mood scores when allopregnanolone serum concentration was in the range of 1.5-2 nmol/l compared to lower and higher concentrations. In addition, women displayed a significant increase in negative mood during the progesterone treatment period, compared to the estradiol-only period when 30 mg progesterone daily was used. On the other hand, treatment with higher doses of progesterone had no influence on negative mood.

CONCLUSIONS

Mood effects during progesterone treatment seem to be related to allopregnanolone concentration, and a bimodal association between allopregnanolone and adverse mood is evident.

Escalated aggressive behavior: Dopamine, serotonin and GABA

The ethical dilemma in aggression research is how to reconcile two divergent objectives, namely to avoid harm and injury as much as possible and, at the same time, how to study behavioral phenomena that validly represent the essence of the neurobiology of aggression. Clinical and preclinical aggression research focuses on different types of aggression. Preclinical studies are usually stimulated by an ethological approach and focus on the phylogeny, ontogeny, survival value and neural mechanisms of ritualized displays and signals. On the other hand, clinical studies focus on violent individuals and pathologically excessive forms of aggressive behavior. This review emphasizes research on escalated forms of aggression in animals and humans and their pharmacotherapy. The current experimental models to generate escalated levels of aggressive behavior in laboratory rely on social instigation, frustrative non-reward and alcohol drinking. These types of aggression are modulated by canonical neurotransmitters like dopamine, serotonin (5-HT) and GABA. It continues to be a main goal of much neurobiological research to find potential targets of pharmacological agents that interact with dopaminergic, GABAergic and serotonergic systems and have high efficacy and selectivity to reduce excessive levels of aggressive and violent behaviors without side-effects. While the mesocorticolimbic dopamine system is implicated in the initiation, execution, termination and consequences of aggressive behavior, drugs with a high affinity for dopamine D2 receptors lack specificity for reducing aggressive behavior. Current investigations point to 5-HT(1B) receptor subtypes as particularly relevant. First, they are differentially expressed in aggression-prone individuals relative to those who are not excessively aggressive. Second, these and also other 5-HT receptor subtypes emerge to be significant targets for anti-aggressive interventions. Positive modulators of GABA(A) receptors with specific subunit configuration may be relevant for heightening aggression, and these sites may be targets for intervention. A prerequisite for rational pharmacotherapies will be adequate characterization of serotonergic and GABAergic receptor regulation in individuals exhibiting escalated aggression.

Neurosteroids, GABAA receptors, and escalated aggressive behavior

Aggressive behavior can serve important adaptive functions in social species. However, if it exceeds the species-typical pattern, it may become maladaptive. Very high or escalated levels of aggressive behavior can be induced in laboratory rodents by pharmacological (alcohol-heightened aggression), environmental (social instigation), or behavioral (frustration-induced aggression) means. These various forms of escalated aggressive behavior may be useful in further elucidating the neurochemical control over aggression and violence. One neurochemical system most consistently linked with escalated aggression is the GABAergic system, in conjunction with other amines and peptides. Although direct stimulation of GABA receptors generally suppresses aggression, a number of studies have found that positive allosteric modulators of GABAA receptors can cause increases in aggressive behavior. For example, alcohol, benzodiazepines, and many neurosteroids are all positive modulators of the GABAA receptor and all can cause increased levels of aggressive behavior. These effects are dose-dependent and higher doses of these compounds generally shift from heightening aggressive behavior to being sedative and anti-aggressive. In addition, these modulators interact with each other and can have additive effects on the GABAA receptor and on behavior, including aggression. The GABAA receptor is a heteropentameric protein that can be constituted from various subunits. It has been shown that subunit composition can affect sensitivity of the receptor to some modulators and that subunit composition differentially affects the sedative vs anxiolytic actions of benzodiazepines. Initial studies targeting alpha subunits of the GABAA receptor point to their significant role in the aggression-heightening effects of alcohol, benzodiazepines, and neurosteroids.

The relation between alcohol and aggression: an integrated biopsychosocial conceptualization

The relation between acute alcohol consumption and aggressive behavior is a complex phenomenon that has been studied from a variety of different disciplines. This article reviews findings from both survey and experimental research. The influence of both situational and individual difference variables on the alcohol-aggression relation is discussed and the strengths and weaknesses of various methodological approaches are highlighted. Current theoretical perspectives of the alcohol-aggression relation are reviewed. An integrated heuristic framework of the alcohol-aggression relation also is outlined. This conceptualization involves both distal and proximal risk factors for problems with alcohol and violence, which include biological, psychological, interpersonal, and contextual influences. Research and treatment implications of this framework are also discussed. It is recommended that researchers attempt to measure variables from a variety of domains in order to obtain a better understanding of this complex phenomenon. Furthermore, it is emphasized that there is a clear need to further implement and assess primary and secondary prevention efforts and to design integrated and flexible approaches for individuals with alcohol and violence problems.

Effects of alcohol on human aggression. Validity of proposed explanations

In the present review, meta-analytic procedures were used to test the validity of three explanations of alcohol-related aggression: physiological disinhibition, expectancy, and indirect cause. According to the physiological disinhibition explanation, alcohol increases aggression directly by anesthetizing the center of the brain that normally inhibits aggressive responding. According to the expectancy explanation, alcohol increases aggression because people expect it to. According to the indirect cause explanation, alcohol increases aggression by causing changes within the person that increase the probability of aggression (e.g., by reducing intellectual functioning). The results from the review were inconsistent with the physiological disinhibition and expectancy explanations, but were consistent with the indirect cause explanation. Experimental manipulations that increased aggression (e.g., provocations, frustrations, aggressive cues) had a stronger effect on intoxicated participants than on sober participants.