An integrative approach to the neurophysiological substrates of social withdrawal and aggression

PTSD and crime propensity: Stress systems, brain structures, and the nature of the relationship

Post-traumatic stress disorder (PTSD) is the most commonly found disorder among the prison population; however, research has been slow to study it as a potential cause of crime. This review examines the neurophysiological changes in the organism associated with PTSD and connects them to crime and antisocial behaviour. Patients with PTSD suffer from a hyperactive sympathetic nervous system (SNS), an overactive amygdala that results in a hypoactive hypothalamic‒pituitary‒adrenal (HPA) axis, and a reduced hippocampal volume. All these features have been separately associated with aggressivity and antisocial behaviour; however, no consensus has been reached. Moreover, very little research has addressed the need to study the interaction between several stress-response systems. As a result, although there is some indication that patients with PTSD are probabilistically more likely to commit acts of crime, no conclusive results on the influence of PTSD on crime propensity can yet be drawn. Future research should address the interaction between the stress-response systems to understand the nature of antisocial behaviour and violence as well as to study any possible links between PTSD prevalence and possible unrest in prisons.

Social withdrawal and testosterone levels in early adolescent boys

Social withdrawal may lead to mental health problems and can have a large impact on a life course, particularly among boys. To support adolescents with social withdrawal, an integrative understanding of the biological bases would be helpful. Social dominance, a possible opposite of social withdrawal, is known to have positive associations with testosterone levels. A previous study suggested that social withdrawal has a negative relationship with sexual maturity among adolescent boys. However, the relationship between social withdrawal and testosterone in adolescence is unknown. This study aimed to examine whether social withdrawal was negatively associated with testosterone levels in early adolescent boys. Salivary samples were collected from 159 healthy early adolescent boys (mean age [standard deviation]: 11.5 [0.73]) selected from participants of the "population-neuroscience study of the Tokyo Teen Cohort" (pn-TTC). Social withdrawal and confounding factors, such as the secondary sexual characteristics and their age in months, were evaluated by self-administered questionnaires completed by the primary parents. The degree of social withdrawal was assessed with the Child Behaviour Checklist (CBCL). Levels of salivary testosterone, and cortisol as a control, were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Logistic regression was conducted to examine the association between social withdrawal and testosterone levels. A higher risk of social withdrawal was associated with a lower salivary testosterone level after adjustment for age in months (odds ratio 0.55, 95 % confidence interval 0.33-0.94), and the association remained significant after adjusting for body mass index, the degree of anxiety/depression and pubertal stage. Thus, we found a negative relationship between social withdrawal and testosterone levels in early adolescent boys. These findings may help to clarify the biological foundations of and to develop support for social withdrawal.

Saliva oxytocin, cortisol, and testosterone levels in adolescent boys with autism spectrum disorder, oppositional defiant disorder/conduct disorder and typically developing individuals

The aim of the current study was to compare levels of oxytocin, cortisol, and testosterone in adolescents with either autism spectrum disorder (ASD), or oppositional defiant disorder (ODD)/conduct disorder (CD), and in typically developing individuals (TDI), and relate hormone levels to severity and subtype of aggression and callous-unemotional (CU) traits. Saliva concentrations of oxytocin, cortisol, and testosterone were assessed in 114 male participants (N = 49 ASD, N = 37 ODD/CD, N = 28 TDI,) aged 12-19 years (M = 15.4 years, SD = 1.9). The ASD and the ODD/CD groups had significantly lower levels of oxytocin than the TDI group, and the ODD/CD group had significantly higher levels of testosterone than the ASD group. There were no group effects on cortisol levels. Group differences remained for oxytocin after correcting for the influence of CU traits, but were not significant after controlling for aggression. Results for testosterone became non-significant after correction for either CU traits or aggression. Across groups, higher levels of CU traits were related to higher levels of cortisol and testosterone, however, proactive and reactive aggression were unrelated to all three hormonal levels. The current findings show that, regardless of cognitive ability or comorbid disorders, the diagnostic groups (ASD, ODD/CD) differ from each other by their hormonal levels, with the ASD group characterized by relative low level of oxytocin, and the ODD/CD group by a relative low level of oxytocin and high level of testosterone. These group effects were partly driven by differences in CU traits between the groups.

Interrelatedness of Children's Psychological and Physiological Responses to Interparental Conflict: A Moderating Role of Harsh Parenting

Children's psychological and physiological responses to interparental conflict have received considerable attention due to their implications for later adjustment, yet limited research has investigated the interplay between these two response systems. This study investigates patterns of association between children's psychological responses (e.g., emotional distress) and cortisol reactivity to interparental conflict, including possible moderations by negative caregiving environment. Participants included 193 families (mother, father, and child). Parents completed questionnaires relating to their caregiving behaviors toward the child (107 girls and 86 boys, M age = 7.99 years, SD = 0.53 years) and children's psychological responses to interparental conflict. Children provided three saliva samples over the course of watching videos depicting conflicts between two adults, whom children were asked to pretend were their parents. Based on a series of Latent Growth Curve Models, only children's emotional responses to interparental conflict (indicated by increased distress) were associated with greater cortisol reactivity. Additionally, fathers' harsh parenting behavior moderated the relation between children's emotional reactivity and cortisol reactivity, yet the moderation effect was not found for mothers' parenting. Findings are discussed in terms of the importance of exploring both psychological and physiological reactivity to conflict and the possible moderating role of harsh parenting.

Gradient of Parvalbumin- and Somatostatin-Expressing Interneurons Across Cingulate Cortex Is Differentially Linked to Aggression and Sociability in BALB/cJ Mice

Successfully navigating social interactions requires the precise and balanced integration of social and environmental cues. When such flexible information integration fails, maladaptive behavioral patterns arise, including excessive aggression, empathy deficits, and social withdrawal, as seen in disorders such as conduct disorder and autism spectrum disorder. One of the main hubs for the context-dependent regulation of behavior is cingulate cortex, specifically anterior cingulate cortex (ACC) and midcingulate cortex (MCC). While volumetric abnormalities of ACC and MCC have been demonstrated in patients, little is known about the exact structural changes responsible for the dysregulation of behaviors such as aggression and social withdrawal. Here, we demonstrate that the distribution of parvalbumin (PV) and somatostatin (SOM) interneurons across ACC and MCC differentially predicts aggression and social withdrawal in BALB/cJ mice. BALB/cJ mice were phenotyped for their social behavior (three-chamber task) and aggression (resident-intruder task) compared to control (BALB/cByJ) mice. In line with previous studies, BALB/cJ mice behaved more aggressively than controls. The three-chamber task revealed two sub-groups of highly-sociable versus less-sociable BALB/cJ mice. Highly-sociable BALB/cJ mice were as aggressive as the less-sociable group-in fact, they committed more acts of socially acceptable aggression (threats and harmless bites). PV and SOM immunostaining revealed that a lack of specificity in the distribution of SOM and PV interneurons across cingulate cortex coincided with social withdrawal: both control mice and highly-sociable BALB/cJ mice showed a differential distribution of PV and SOM interneurons across the sub-areas of cingulate cortex, while for less-sociable BALB/cJ mice, the distributions were near-flat. In contrast, both highly-sociable and less-sociable BALB/cJ mice had a decreased concentration of PV interneurons in MCC compared to controls, which was therefore linked to aggressive behavior. Together, these results suggest that the dynamic balance of excitatory and inhibitory activity across ACC and MCC shapes both social and aggressive behavior.

Social instigation and repeated aggressive confrontations in male Swiss mice: analysis of plasma corticosterone, CRF and BDNF levels in limbic brain areas

Introduction:

Agonistic behaviors help to ensure survival, provide advantage in competition, and communicate social status. The resident-intruder paradigm, an animal model based on male intraspecific confrontations, can be an ethologically relevant tool to investigate the neurobiology of aggressive behavior.

Objectives:

To examine behavioral and neurobiological mechanisms of aggressive behavior in male Swiss mice exposed to repeated confrontations in the resident intruder paradigm.

Methods:

Behavioral analysis was performed in association with measurements of plasma corticosterone of mice repeatedly exposed to a potential rival nearby, but inaccessible (social instigation), or to 10 sessions of social instigation followed by direct aggressive encounters. Moreover, corticotropin-releasing factor (CRF) and brain-derived neurotrophic factor (BNDF) were measured in the brain of these animals. Control mice were exposed to neither social instigation nor aggressive confrontations.

Results:

Mice exposed to aggressive confrontations exhibited a similar pattern of species-typical aggressive and non-aggressive behaviors on the first and the last session. Moreover, in contrast to social instigation only, repeated aggressive confrontations promoted an increase in plasma corticosterone. After 10 aggressive confrontation sessions, mice presented a non-significant trend toward reducing hippocampal levels of CRF, which inversely correlated with plasma corticosterone levels. Conversely, repeated sessions of social instigation or aggressive confrontation did not alter BDNF concentrations at the prefrontal cortex and hippocampus.

Conclusion:

Exposure to repeated episodes of aggressive encounters did not promote habituation over time. Additionally, CRF seems to be involved in physiological responses to social stressors.

Altered Hippocampal Neurogenesis and Amygdalar Neuronal Activity in Adult Mice with Repeated Experience of Aggression

Repeated experience of winning in a social conflict setting elevates levels of aggression and may lead to violent behavioral patterns. Here, we use a paradigm of repeated aggression and fighting deprivation to examine changes in behavior, neurogenesis, and neuronal activity in mice with positive fighting experience. We show that for males, repeated positive fighting experience induces persistent demonstration of aggression and stereotypic behaviors in daily agonistic interactions, enhances aggressive motivation, and elevates levels of anxiety. When winning males are deprived of opportunities to engage in further fights, they demonstrate increased levels of aggressiveness. Positive fighting experience results in increased levels of progenitor cell proliferation and production of young neurons in the hippocampus. This increase is not diminished after a fighting deprivation period. Furthermore, repeated winning experience decreases the number of activated (c-fos-positive) cells in the basolateral amygdala and increases the number of activated cells in the hippocampus; a subsequent no-fight period restores the number of c-fos-positive cells. Our results indicate that extended positive fighting experience in a social conflict heightens aggression, increases proliferation of neuronal progenitors and production of young neurons in the hippocampus, and decreases neuronal activity in the amygdala; these changes can be modified by depriving the winners of the opportunity for further fights.

Effects of adverse early-life events on aggression and anti-social behaviours in animals and humans

We review the impact of early adversities on the development of violence and antisocial behaviour in humans, and present three aetiological animal models of escalated rodent aggression, each disentangling the consequences of one particular adverse early-life factor. A review of the human data, as well as those obtained with the animal models of repeated maternal separation, post-weaning social isolation and peripubertal stress, clearly shows that adverse developmental conditions strongly affect aggressive behaviour displayed in adulthood, the emotional responses to social challenges and the neuronal mechanisms activated by conflict. Although similarities between models are evident, important differences were also noted, demonstrating that the behavioural, emotional and neuronal consequences of early adversities are to a large extent dependent on aetiological factors. These findings support recent theories on human aggression, which suggest that particular developmental trajectories lead to specific forms of aggressive behaviour and brain dysfunctions. However, dissecting the roles of particular aetiological factors in humans is difficult because these occur in various combinations; in addition, the neuroscientific tools employed in humans still lack the depth of analysis of those used in animal research. We suggest that the analytical approach of the rodent models presented here may be successfully used to complement human findings and to develop integrative models of the complex relationship between early adversity, brain development and aggressive behaviour.

Long-term neuroendocrine effects of iron-deficiency anemia in infancy

INTRODUCTION

Iron-deficiency anemia (IDA) is recognized to have long-lasting effects on neurodevelopment, but there is little research on neuroendocrine systems.

METHODS

This study examined the effects of IDA in early or later infancy on plasma cortisol and prolactin stress-response patterns for 1 h after a venipuncture and catheter placement in 10-y-old healthy Chilean children. Children identified with IDA at 6 mo (IDA-6; n = 13) or 12 mo (IDA-12; n = 24) and who were iron sufficient (IS) at other infancy time points were compared to children who were IS at all time points during infancy (n = 23). All children received at least 6 mo of oral iron treatment in infancy.

RESULTS

At 10 y of age, IDA-6 and IDA-12 children demonstrated altered cortisol response patterns; both showed a more immediate decline and IDA-12 children showed a blunted curvature as compared to IS children. IDA-12 children showed significantly lower cortisol levels at 30 and 45 min after venipuncture and catheter placement than did IS children. There were no significant differences for stress-responsive plasma prolactin patterns between groups.

DISCUSSION

The results indicate that having IDA during infancy is associated with long-term neuroendocrine effects on stress-responsive cortisol patterns.

Visually detected NREM Stage 2 sleep spindles in kindergarten children are associated with stress challenge and coping strategies

OBJECTIVES

Sleep EEG spindles are linked to efficient cortical-subcortical connectivity and intellectual abilities. The aim of the present study was to investigate the relationship of spindle activity to psychosocial stress response and coping strategies in healthy kindergarten children.

METHODS

In a cross-sectional study of 41 5-year old kindergarten children we examined stress-induced hypothalamic-pituitary-adrenocortical (HPA) system activity by saliva cortisol measurements and sleep regulation by sleep EEG-monitoring. Stress response was measured during the application of a standardized psychological challenge appropriate at this age. NREM S2 sleep EEG spindles were visually scored and put into relation to coping and HPA activity parameters.

RESULTS

An increased total number of NREM S2 sleep spindles correlated positively with increased high ego-involvement strategies such as "positive emotions". By contrast, total number of NREM S2 sleep spindles correlated negatively with low ego-involvement strategies such as "denial" and "avoidance". Stress induced HPA-activity correlated positively with coping strategies with high ego-involvement; while there was no correlation with low ego-involvement strategies.

CONCLUSIONS

Total number of visually detected NREM S2 sleep spindles is elevated in children with coping involving positive, high ego-involvement; in contrast, low ego-involvement during stress is associated with reduced total number of NREM S2 sleep spindles.

Interparental aggression and children's adrenocortical reactivity: testing an evolutionary model of allostatic load

Guided by an evolutionary model of allostatic load, this study examined the hypothesis that the association between interparental aggression and subsequent changes in children's cortisol reactivity to interparental conflict is moderated by their temperamental dispositions. Participants of the multimethod, longitudinal study included 201 2-year-old toddlers and their mothers. These children experienced elevated levels of aggression between parents. Consistent with the theory, the results indicated that interparental aggression predicted greater cortisol reactivity over a 1-year period for children who exhibited high levels of temperamental inhibition and vigilance. Conversely, for children with bold, aggressive temperamental characteristics, interparental aggression was marginally associated with diminished cortisol reactivity. Further underscoring its implications for allostatic load, increasing cortisol reactivity over the one year span was related to concomitant increases in internalizing symptoms but decreases in attention and hyperactivity difficulties. In supporting the evolutionary conceptualization, these results further supported the relative developmental advantages and costs associated with escalating and dampened cortisol reactivity to interparental conflict.

The effect of trauma on stress reactivity in aggressive youth

To address gaps in the literature related to the contribution of childhood trauma on aggression, we evaluated salivary cortisol and heart rate changes to psychological challenge in aggressive children with various degrees of trauma. We hypothesized that traumatized and aggressive youths will exhibit higher responsiveness to an active challenge (Violent film-VF) than aggressive youth with no trauma but will not differ when viewing a Non-Violent film (NVF). A total of 25 children (aged 9-12; M=15, F=9) with history of aggression were assessed for trauma exposure. Children viewed the two films in randomized order. Four salivary cortisol and pulse measurements were obtained before (T1), 15 min after the start (T2), at the end (T3), and 15 min following the end of the movie (T4). Repeated measures Analysis of Covariance (ANCOVA) using Film (VF/NVF), Cortisol/Time at T1-T4, Group (Trauma/Non-Trauma), and Film Order were performed with age and gender as covariates. There were significant main effects for Group and Cortisol/Time for the Trauma group showing greater cortisol responsiveness than the Non-Trauma group that was most pronounced during the NVF. These results suggest that aggressive youth with personal history of trauma may exhibit unique biological characteristics, which may have important implications for classification and treatment.

Family relationships and children's stress responses

In this chapter, the theoretical and empirical associations between family relationships and children's responses to stressors are reviewed. Family relationships explored are primarily dyadic, representing the emphasis of past empirical research; these include parent-parent, parent-child, and sibling relationships. However, in recognition of the more complicated and interconnected nature of family relationships, also reviewed are associations between the broader family context and children's stress responses. Multiple measures of stress responses are considered, including both physiological and emotional responses to and recovery from stressful experiences. Overall, the studies reviewed suggest that poor-quality family environments, including those characterized by low emotional support or high conflict, are associated with dysregulated stress responses throughout childhood and adolescence. In contrast, children and adolescents in families with high emotional support or low conflict seem to be protected from developing stress regulatory problems. Limitations in this body of research as well as directions for future research are discussed.

Children's noncompliance during saliva collection predicts measures of salivary cortisol

Salivary cortisol has been useful for evaluating children's physiological responses to stress and for identifying factors that predict their magnitude and duration. However, results have been somewhat equivocal across studies, and this has motivated researchers to identify sources of variance and error. Here, we examined the prevalence of preschoolers' noncompliance during saliva collection and aimed to learn about noncompliant children in terms of their hypothalamus-pituitary-adrenal function, behavior in other situations, and symptoms of behavioral problems. Results were based on measures of cortisol, children's behavior during saliva collection and a mother-child teaching interaction, and ratings of problem behavior by teachers and parents. Results show that 12% (21/174) of the sample was noncompliant on at least one of the collection trials. Children, who were noncompliant but did not outright refuse saliva collection, had higher cortisol than did compliant children. Children who were noncompliant during saliva collection were likely to be noncompliant during the teaching episode, and they were perceived as having more internalizing symptoms than compliant children. These results suggest that children's noncompliance during saliva collection can be a source of nonrandom missing data or extreme cortisol values, which should be considered in future studies.

Behavioural inhibition: is it a risk factor for anxiety?

Behavioural inhibition is a stable temperamental trait that is identifiable during infancy and toddlerhood and is characterized by fearful reactivity to novelty. Children identified as behaviourally inhibited have been shown to be at increased risk for developing anxiety disorders such as social phobia. The current review addresses the link between behavioural inhibition and the risk for developing anxiety disorders. Research suggests that this risk may be modulated by a number of extrinsic and intrinsic factors. Extrinsic factors include particular parental beliefs, parenting styles, and childrearing contexts. Intrinsic factors include executive function capacities such as attention bias, attention shifting, inhibitory control, and self-monitoring. In the present paper we review the contribution of these factors to the development of anxiety in behaviourally inhibited children.

Children's internalizing symptoms: the role of interactions between cortisol and respiratory sinus arrhythmia

We examined interactions between children's physiological activity across two systems, the hypothalamic-pituitary-adrenal (HPA)-axis and the parasympathetic nervous system (PNS), as predictors of child-reported internalizing symptoms (depression, anxiety). HPA activity was indexed by baseline salivary cortisol, and PNS activity was indexed by baseline respiratory sinus arrhythmia (RSA). Study 1 consisted of 57 children (54% girls; M age=8.81 years ±.34), and Study 2 included 219 children (51% girls; M age=9.31 years ±.79). Cortisol interacted with RSA to explain unique variance in children's internalizing symptoms. Across the two studies, children with higher cortisol levels in conjunction with higher RSA levels tended to exhibit the lowest levels of depression and anxiety symptoms. Findings demonstrate that contemporaneous consideration of physiological activity across multiple systems can advance understanding of internalizing symptoms in children.

Sleep actigraphy pattern and behavioral/emotional difficulties in kindergarten children: association with hypothalamic-pituitary-adrenocortical (HPA) activity

BACKGROUND

Various studies of adult endocrinology and sleep show close connections between poor sleep quality, deterioration of the HPA axis and negative psychological characteristics. However, the extent to which these associations may have already emerged and developed in childhood remains unclear.

METHODS

A total of 82 preschoolers (age 4.91+/-0.48) underwent activity monitoring for seven consecutive days and nights, wearing a digital movement-measuring instrument. Additionally, on the first and on the last morning of sleep registration, the activity of the HPA axis was assessed via the amount of cortisol in the saliva. Psychological and behavioral assessments were also made.

RESULTS

Three sub-groups of good (22%), normal (58.5%) and poor (19.5%) sleepers were distinguished. Poor sleep patterns were associated with higher HPA activity and with behavioral/emotional difficulties.

CONCLUSIONS

The interplay between unfavorable sleep patterns, deterioration of the HPA axis and behavioral/emotional difficulties is already apparent in pre-school children.

Cortisol awakening response in healthy children and children with ADHD: impact of comorbid disorders and psychosocial risk factors

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common child psychiatric disorders. Previous studies have reported a blunted cortisol response to challenging situations and a decreased cortisol awakening response (CAR) in children with ADHD. As ADHD often is comorbid with oppositional defiant disorder (ODD), conduct disorder (CD), or anxiety disorder (AnxD), and changes in hypothalamic-pituitary-adrenal (HPA) axis activity have also been reported for these disorders, the present study aimed to compare the CAR in children with ADHD with and without comorbid disorders. Data on the CAR were obtained in 128 children with ADHD (aged 6-13 years) and in 96 control children (aged 6-12 years). Children with ADHD+ODD showed an attenuated CAR (area under the curve, AUC) compared to children with ADHD without ODD/CD and control children. Findings point towards either disinhibition or pervasive underarousal in children with ADHD+ODD, and seem to be specific for children with ADHD+ODD, as the attenuated CAR-AUC was not observed in children with ADHD without comorbid disorders or children with ADHD+CD or ADHD+AnxD. In addition, current adverse parenting conditions, family conflicts, and acute life events were associated with mean increase in CAR, emphasizing the role of psychosocial risk factors in mediating HPA axis activity in children with ADHD.

Individual differences in cortisol responses to fear and frustration during middle childhood

The purpose of this study was to examine individual differences in the activation and regulation of the hypothalamic-pituitary-adrenal (HPA) axis in prepubertal children after exposure to two different stress modalities and to evaluate the utility of an individual differences approach to the examination of HPA axis functioning. After a 30-min controlled baseline period, 73 7-year-olds (40 boys and 33 girls) were randomly assigned to a validity check condition or one of two experimental tasks designed to elicit fear or frustration. This was followed by a 60-min controlled regulation phase. A total of 17 saliva samples were collected, including 12 poststress samples at 5-min intervals. There was a significant stress modality effect, with children exposed to the fear condition reaching peak cortisol levels at 25min poststress and those exposed to the frustration condition reaching peak levels at 45min poststress. There was no difference in peak cortisol levels between the stress modalities. Individual variability across conditions was significant, with participants reaching peak levels as early as 10min poststress and as late as 60min poststress. Our data suggest that analysis of individual curves prior to making group-level comparisons may improve the explanatory power of HPA axis behavior models.

The role of child adrenocortical functioning in pathways between interparental conflict and child maladjustment

This study examined the interplay between interparental conflict and child cortisol reactivity to interparental conflict in predicting child maladjustment in a sample of 178 families and their kindergarten children. Consistent with the allostatic load hypothesis (McEwen & Stellar, 1993), results indicated that interparental conflict was indirectly related to child maladjustment through its association with individual differences in child cortisol reactivity. Analyses indicated that the multimethod assessment of interparental conflict was associated with lower levels of child cortisol reactivity to a simulated phone conflict between parents. Diminished cortisol reactivity, in turn, predicted increases in parental reports of child externalizing symptoms over a 2-year period. Associations between interparental conflict, child cortisol reactivity, and child externalizing symptoms remained robust even after demographic factors and other family processes were taken into account.

Acute effects of AMPA-type glutamate receptor antagonists on intermale social behavior in two mouse lines bidirectionally selected for offensive aggression

Involvement of AMPA-type glutamate receptors in the regulation of social behavior has been suggested by experiments with mice deficient for the GluR-A subunit-containing AMPA receptors showing reduced intermale aggression. In the present study, effects of AMPA receptor antagonists on mouse social behavior towards unfamiliar Swiss-Webster males on a neutral territory were tested using male subjects from the Turku Aggressive (TA) and Turku Non-Aggressive (TNA) mouse lines bidirectionally selected for high and low levels of offensive aggression. The drugs were the competitive antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX), and the non-competitive antagonist 4-(8-methyl-9H-1,3-dioxolo[4,5-h][2,3]benzodiazepin-5-yl)-benzenamine (GYKI 52466). In TA mice, CNQX and NBQX decreased the biting component of aggressive structure, while GYKI 52466 suppressed all aggressive manifestations. All drugs increased anxiety-like behavior towards the partner. In TNA mice, NBQX activated mouse social behavior and ambivalent aggression, while CNQX and GYKI 52466 only increased anxiety. Thus, AMPA receptor antagonists affect aggressive behaviors in TA mice supporting the idea that AMPA receptors are involved in the modulation of agonistic impulsive behavioral pattern. GYKI 52466 appeared to be the most selective and efficacious in suppressing the aggression.

Social behavior and cortisol reactivity in children with fragile X syndrome

OBJECTIVE

To examine the association between limbic-hypothalamic-pituitary-adrenal (L-HPA) axis reactivity and social behavior in children with fragile X syndrome (FXS).

METHOD

Salivary cortisol changes and concurrent anxiety-related behaviors consistent with the behavioral phenotype of FXS were measured in 90 children with the fragile X full mutation and their 90 unaffected siblings during a social challenge task in the home.

RESULTS

Boys and girls with FXS demonstrated more gaze aversion, task avoidance, behavioral signs of distress, and poorer vocal quality than the unaffected siblings. Multiple regression analyses showed that after accounting for effects of IQ, gender, age, quality of the home environment, and basal cortisol level, cortisol reactivity to the task was significantly associated with social gaze in children with FXS. The most gaze-aversive children with FXS had cortisol reductions, whereas those with more eye contact demonstrated the most cortisol reactivity. Unaffected siblings demonstrated an opposite pattern in which less eye contact was associated with increased cortisol reactivity.

CONCLUSIONS

Results of the study suggest a unique relation between abnormal gaze behavior and L-HPA mediated stress reactivity in FXS.

Progestin concentrations are increased following paced mating in midbrain, hippocampus, diencephalon, and cortex of rats in behavioral estrus, but only in midbrain of diestrous rats

BACKGROUND

The progesterone (P(4)) metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP), acts in the midbrain ventral tegmental area (VTA) to modulate the intensity and duration of lordosis. 3alpha,5alpha-THP can also have anti-anxiety and anti-stress effects in part through actions in the hippocampus. Separate reports indicate that manipulating 3alpha,5alpha-THP levels in the VTA or hippocampus respectively can influence lordosis and affective behavior. 3alpha,5alpha-THP levels can also be altered by behavioral experiences, such as mating or swim stress. Whether endogenous levels of 3alpha,5alpha-THP modulate and/or are increased in response to affective and/or reproductively-relevant behaviors was investigated.

METHODS

In Experiment 1, rats in behavioral estrus or diestrus were individually tested sequentially in the open field, elevated plus maze, partner preference, social interaction, and paced mating tasks and levels of 17beta-estradiol (E(2)), P(4), dihydroprogesterone (DHP), and 3alpha,5alpha-THP in serum, midbrain, hippocampus, diencephalon, and cortex were examined. In Experiments 2 and 3, rats in behavioral estrus or diestrus, were individually tested in the battery indicated above, with, or without, paced mating and tissues were collected immediately after testing for later assessment of endocrine measures.

RESULTS

In Experiment 1, behavioral estrous, compared to diestrous, rats demonstrated more exploratory, anti-anxiety, social, and reproductive behaviors, and had higher levels of E(2) and progestins in serum, midbrain, hippocampus, diencephalon, and cortex. In Experiment 2, in midbrain and hippocampus, levels of 3alpha,5alpha-THP and its precursor DHP were increased among rats in behavioral estrus that were mated. In diencephalon, and cortex, DHP levels were increased by mating. In Experiment 3, in midbrain, levels of 3alpha,5alpha-THP and its precursor DHP were increased among diestrous rats that were tested in the behavioral battery with mating as compared to those tested in the behavioral battery without mating.

CONCLUSIONS

Increased levels of 3alpha,5alpha-THP in behavioral estrus versus diestrous rats are associated with enhanced exploratory, anti-anxiety, social, and reproductive behaviors. Rats in behavioral estrus that are mated have further increases in 3alpha,5alpha-THP and/or DHP levels in midbrain, hippocampus, diencephalon, and cortex than do non-mated rats in behavioral estrus, whereas diestrous rats only show 3alpha,5alpha-THP increases in midbrain in response to behavioral testing that included mating.