Neuropharmacological aspects of adaptive pain inhibition in murine “victims” of aggression

This review outlines recent research on a subset of physiological responses in murine “victims” or aggression. In a typical resident-intruder paradigm, the detailed study of intruders has revealed that exposure to conspecific attack (and related stimuli) is associated with two forms of analgesia which appear to be integral components of the murine defensive repertoire. In response to intense/enduring attack, intruder mice display a profound, long-lasting and opioid-mediated analgesia. This reaction is highly correlated with defensive immobility and may function to reduce involuntary cues to further attack. In contrast, the inhibition of pain reactivity in mice tested immediately upon the display of defeat is less intense, shorter-lasting, non-opioid in nature and may function to facilitate active defenses such as escape. As this form of pain inhibition is also evident in intruders exposed to the scent of an aggressive male conspecific, a possible anticipatory defensive function linked to mechanisms of anxiety has been proposed. This hypothesis is supported by 1) the prevention of defeat analgesia by a range of antianxiety drugs (benzodiazepines, 5-hydroxytryptamine_1A [5-HT_1A] receptor agonists, and 5-HT₃ receptor antagonists) and 2) the effects of social defeat on behavior in the elevated plusmaze model of anxiety. These findings are discussed in relation to coping mechanisms in murine “victims” of aggression. © 1995 Wiley-Liss, Inc.     

Infants of “depressed” mothers interact better with their nondepressed fathers

To determine whether infants of “depressed” mothers interact better with their nondepressed fathers, twenty-six 3- to 6-month-old infants were videotaped during face-to-face interactions with their parents. The “depressed” mother group consisted of twelve 3- to 6-month-old infants and their “depressed” mothers and nondepressed fathers. The control group was composed of 14 nondepressed mothers and nondepressed fathers and their 3- to 6-month-old infants. In the “depressed” mother group, the nondepressed fathers received better interaction ratings than the “depressed” mothers. In turn, the infants received better interaction ratings when they interacted with their nondepressed fathers than with their “depressed” mothers. In contrast, nondepressed fathers and mothers and their infants in the control group did not differ on any of their interaction ratings. These findings suggest that infants' difficult interaction behaviors noted during interactions with their “depressed” mothers may not extend to their nondepressed fathers. The data are discussed with respect to the notion that nondepressed fathers may “buffer” the effects of maternal depression on infant interaction behavior.     

Does community violence exposure moderate the associations between maternal spanking and early child behavior problems?

A robust research literature links parental spanking with negative behavioral outcomes for children, however, it remains unclear whether conditions in the community may moderate the associations between spanking and behavior problems in early childhood. In the current study, we examined whether community violence exposure moderated the associations of maternal spanking with externalizing and internalizing behavior problems of young children. The sample used in this study was urban families and their children ages 3–5 (n = 2,472). We used fixed effects regression models, which yield stronger statistical control for baseline behavior problems, selection bias, and omitted variables bias. Mother's spanking was associated with elevated levels of both externalizing (β = .037, p < .001) and internalizing (β = .016, p < .001) behavior problems. Community violence exposure also predicted higher levels of externalizing (β = .071, p < .01) and internalizing (β = .043, p < .05) behavior problems. Community violence exposure did not moderate the associations between maternal spanking and behavior problems. Professionals working with families should promote the use of nonphysical disciplinary practices, regardless of the level of violence and crime in the community in which the family resides.     

When is it Okay to be Alone? Gender Differences in Normative Beliefs about Social Withdrawal in Emerging Adulthood

Sex Roles - Informed by prior work on social withdrawal and gender role norms, the present study utilizes data from a large sample of U.S. (n?=?656) and Canadian (n?=?560)...     

The medial amygdala: Serotonergic inhibition of shock-lnduced aggression and pain sensitivity in rats

Two aspects of the amygdaloid complex (corticomedial and basolateral) were examined with reference to serotonergic inhibition of shock-induced aggression. Fighting was significantly depressed by serotonergic stimulation (5-HT, 10 μg bilateral) in the corticomedial amygdala while serotonergic blockade (methysergide, 5 μg bilateral) in this region increased levels of fighting. No consistent effects were obtained with serotonergic manipulation of the basolateral amygdala. Further investigation revealed that the state of serotonergic activity in medial amygdaloid sites was associated with concomitant alterations in the animals' sensitivity to footshock. Results are discussed in relation to a) a general inhibitory role of serotonin in behavioural mechanisms and b) a dopaminergic-serotonergic balance for behavioural arousal involving medial amygdaloid nuclei.     

Alterations in shock-induced fighting and locomotor activity following intracerebroventricular injection of hydrocortisone in the rat

Three experiments were conducted in an attempt to clarify the facilitatory influence of hydrocortisone on shock-induced fighting in rats. Results of the first experiment indicated a biphasic, dose-dependent action of intraventricularly-administered hydrocortisone. Low (25 μg) and intermediate (50 μg) doses both facilitated fighting whilst the high (100 μg) dose exerted a potent suppressant effect. Two control tests were performed to determine whether alterations in pain reactivity or locomotor activity could have accounted for the observed changes in fighting behaviour. None of the treatments altered shock thresholds (Experiment 2) but whilst neither low nor intermediate doses affected activity measures, the high dose preferentially reduced vertical activity (Experiment 3).     

Do boys with attention-deficit/hyperactivity disorder have positive illusory self-concepts?

One hundred ninety-five boys with attention-deficit/hyperactivity disorder (ADHD) were compared with 73 comparison boys (M = 9.83 years, SD = 1.30) on self-perceptions relative to a teacher-rated criterion. Emphasis was placed on ADHD subgroup comparisons according to level of aggression, academic achievement, and depression compared with control boys. Consistent with the authors' prediction, ADHD boys overestimated relative to teacher report, more than did controls, in the scholastic competence, social acceptance, and behavioral conduct domains. Examination of discrepancy scores (child rating - teacher rating) by comorbidity subgroups suggested that aggressive and low-achieving ADHD boys tended to overestimate their competence the most in the domains in which they were the most impaired. Results are discussed in terms of prior literature on "positive illusions" in ADHD children.