Ontogeny of sex differences in defensive burying behavior in rats: effect of social isolation

Abstract

The aim of the present experiments was to clarify sex differences in socio-developmental factors that affected defense behavior in rats. Sex differences in the defensive burying behavior of rats, and related social factors, were explored in three developmental stages: juvenile, puberty, and adult; 30, 50, and 80 days of age, respectively. The duration of burying, digging into bedding material, stretch-attend postures, and crouch/freezing were measured in a shock-prod test. For males, the duration of burying was longer in the juvenile and pubertal stages than in adulthood. For females, no age differences in the duration of burying were found. Males showed longer burying durations than females in both the juvenile and pubertal stages. For both sexes, the highest duration of digging was found in the juvenile stage, and females showed longer durations of digging than males. Both male and female rats isolated during the juvenile stage, from 26 to 40 days of age, showed smaller durations of burying behavior compared to pair-reared rats. This effect of juvenile isolation was maintained among both adult males and females even when they were returned to pair rearing after isolation. Isolation during adulthood, from 66 to 80 days of age, increased burying behavior in males, but decreased it in females. The durations of digging, stretch-attend postures, and crouch/freezing were not affected by isolation. The decrease in defensive burying and its increase resulting from isolation in adult male rats, suggest that the emergence of adult-like social relationships in males suppressed the duration of burying. Male and female rats isolated during the juvenile stage maintained lower levels of burying, suggesting that social experience as juveniles is important for the emergence of defensive burying behavior.

Early Adolescence as a Critical Window During Which Social Stress Distinctly Alters Behavior and Brain Norepinephrine Activity

“…That this effect was not reproduced by restraint indicates that it is selective to social stress. The findings are consistent with studies showing that group housing adult male rats, which involves the establishment of social hierarchies, decreases defensive burying compared to isolation housing (Arakawa, 2007a, b). The interpretation of those findings was that social stress decreased proactive defensive behaviors and increased reactive behaviors.…”

“…Housing conditions were comparable for the resident-intruder stress, the restraint stress and the exposure to peer experiments, yet the behavioral effects were only observed in the resident-intruder stress group. Most importantly, social isolation of EA and adult rats has effects on defensive burying that are opposite to those produced by the resident-intruder stress in this study (Arakawa, 2007a, b). Thus, isolation housing of EA rats inhibited defensive burying and isolation housing of adults increased defensive burying.…”

Conserved Serotonergic Background of Experience-Dependent Behavioral Responsiveness in Zebrafish ( Danio rerio )

“…On the other hand, isolation-induced low avoidance has also been interpreted as reduced proactive coping in rodents. Isolated rats consistently showed adversity-dependent delay in exploration, indicating a stress-related incapability of challenge responsiveness (Arakawa, 2005(Arakawa, , 2007. Also, zebrafish individuals that show delayed emergence from a dark to a brightly lit arena, a phenotype resembling the one observed in our study, showed lower locomotion in general and lower challenge-induced but similar baseline HPA axis activity (Tudorache et al, 2015).…”

Age‐dependent change in exploratory behavior of male rats following exposure to threat stimulus: Effect of juvenile experience

“…Based on the hypothesis that mild shock as an aversive stimulus which induces increment of anxiety (McBlane & Handley, 1994; and motivation to assess the risk in the environment (Blanchard, Blanchard, & Rodgers, 1991), it is likely that alteration in the behavioral patterns as a response to mild threats occurs during puberty should be responsible for the developmental change in the direction of response to mild shock. Proactive defense style which associated with increased active exploration and offensive aggression when animals are confronted with mild threat stimulus, emerges during adolescence (Arakawa, 2005b(Arakawa, , 2007Palanza, 2001;Spear, 2000). Perhaps, male rats reared in isolation during the juvenile stage did not show this emergence of proactive defense style.…”