Disruption of the vasopressin 1b receptor gene impairs the attack component of aggressive behavior in mice

Abstract

Vasopressin affects behavior via its two brain receptors, the vasopressin 1a and vasopressin 1b receptors (Avpr1b). Recent work from our laboratory has shown that disruption of the Avpr1b gene reduces intermale aggression and reduces social motivation. Here, we further characterized the aggressive phenotype in Avpr1b 2/2 (knockout) mice. We tested maternal aggression and predatory behavior. We also analyzed the extent to which food deprivation and competition over food increases intermale aggression. We quantified defensive behavior in Avpr1b 2/2 mice and later tested offensive aggression in these same mice. Our results show that attack behavior toward a conspecific is consistently reduced in Avpr1b 2/2 mice. Predatory behavior is normal, suggesting that the deficit is not because of a global inability to detect and attack stimuli. Food deprivation, competition for food and previous experience increase aggression in both Avpr1b 1/1 and 2/2 mice. However, in these circumstances, the level of aggression seen in knockout mice is still less than that observed in wild-type mice. Defensive avoidance behaviors, such as boxing and fleeing, are largely intact in knockout mice. Avpr1b 2/2 mice do not display as many 'retaliatory' attacks as the Avpr1b 1/1 mice. Interestingly, when territorial aggression was measured following the defensive behavior testing, Avpr1b 2/2 mice typically show less initial aggressive behavior than wildtype mice, but do show a significant increase in aggression with repeated testing. These studies confirm that deficits in aggression in Avpr1b 2/2 mice are limited to aggressive behavior involving the attack of a conspecific. We hypothesize that Avpr1b plays an important role in the central processing that couples the detection and perception of social cues (which appears normal) with the appropriate behavioral response.

Reduced ultrasonic vocalizations in vasopressin 1b knockout mice

“…Fewer vocalizations to social stimuli emitted by Avpr1b −/− virgin females in the present study is consistent with recent data on maternal aggression to a male intruder in the same line of mutant mice [51]. Avpr1b −/− lactating females displayed significantly fewer attacks on a male intruder, suggestive of a reduced response to social cues, leading to a reduced nest defense.…”

“…Vasopressin systems have been implicated in aspects of rodent social interaction, including aggression, social recognition, and interest in social olfactory cues [5,6,13,14,16,18,48,[51][52][53]. The present experiments addressed the question of whether vocalizations emitted within social contexts in adult and infant mice require the vasopressin 1b receptor subtype.…”

“…The present experiments addressed the question of whether vocalizations emitted within social contexts in adult and infant mice require the vasopressin 1b receptor subtype. Null mutation of the Avpr1b gene was previously reported to reduce aggression in male mice in the resident-intruder task [51][52][53]. In contrast to male residents, female resident mice usually display more social investigation and less attack behavior toward a female intruder mouse [11,32].…”

“…Oxytocin knockout mice revealed the role of oxytocin in mediating social recognition, social memory, aggression, maternal behaviors, and ultrasonic vocalizations by pups separated from the nest [5,10,29,39,42,57]. Vasopressin receptor subtype V1a (Avpr1a) knockout mice displayed impaired social recognition and low anxiety-like behaviors [4,5,12], and reduced responses to social olfactory cues [51]. Higher levels of the…”

Genetic and non-genetic determinants of aggression in combat sports

“…Wersinger et al [95] examined maternal aggression and predatory behavior in knockout mice with genotype AVPR1B −/− , i.e. with the AVPR1B gene removed.…”