The influence of puberty on stress reactivity and forebrain glucocorticoid receptor levels in inbred and outbred strains of male and female mice.

OBJECTIVE: To examine stress-induced corticosterone responses and forebrain glucocorticoid receptor (GR) levels in prepubertal and adult, male and female mice of three commonly used inbred (C57BL/6, BALB/c) and outbred (Swiss Webster) strains.
METHODS: Prepubertal (30 days of age) and adult (75 days of age), male and female C57BL/6, BALB/c, and Swiss Webster mice were exposed to a 30 min session of restraint stress. Plasma corticosterone was measured before (basal), or 0, 30, or 60 min after termination of the stressor. GR protein levels of the medial prefrontal cortex, paraventricular nucleus of the hypothalamus, and hippocampus were also measured via tissue punches and western blots in the prepubertal and adult males and females at the basal time point.
RESULTS: In response to acute stress, prepubertal males of both inbred strains showed greater hormonal responsiveness than their adult counterparts, while females of these strains displayed similar stress-induced corticosterone responses, independent of age. Conversely, only the females of the outbred Swiss Webster strain showed pubertal-related changes, with adult females showing greater hormonal reactivity compared to prepubertal females. Despite these significant differences in hormonal reactivity, we found little difference in GR protein levels in the brain regions examined.
CONCLUSIONS: These data indicate that pubertal-dependent differences in stress reactivity can be significantly influenced by sex and genetic background. Moreover, these data provide points of departure for future studies investigating how puberty, sex, and genetic background interact to shape both short- and long-term effects of stress on mental and physical health.