Marked regulatory shifts in gonadal, adrenal, and metabolic system responses to repeated restraint stress occur within a 3-week period in pubertal male rats.

We compared testosterone (T), corticotropin (ACTH), corticosterone (B), and leptin responses to three daily 3-h bouts of restraint and blood sampling as well as energy balance of male rats in early (40 d of age) and late (60 d of age) puberty. Rats either remained intact or were adrenalectomized and replaced with B clamped at basal mean values (ADX+B). Hormones, weight gain, food intake, and fat depot weight were measured during or after the days of stress. The major effects of restraint on T, ACTH, and energetic responses were age dependent, but clamped B affected the effects of restraint seen in intact rats at each age. T secretion was inhibited in 40-d-old and was stimulated in 60-d-old rats after restraint. ACTH responses were high, but diminished with repetition of stress in intact, but not ADX+B, 40-d-old rats. ACTH responses were lower, but constant across days, in both intact and ADX+B 60-d-old rats. Younger rats gained weight during the period of stress, whereas older rats stopped gaining weight. We conclude that the central regulation of stress responses shifts markedly between early and late puberty, although stress-induced B responses are important at both ages. In early puberty, priority is placed on maintaining normal ponderal growth, whereas in late puberty, priority is placed on maintaining reproductive capability.