Behavioral and corticotropic effects of ACTH during early postnatal ontogeny in rats.

ACTH1-24(1 mg/kg) administered to 5-7-day-old rats reduced their locomotor activity and did not alter blood levels of corticosterone. ACTH administration on postnatal days 12-14 increased corticosterone levels, but had no effect on locomotor activity. Thus, the behavioral effect of ACTH is not due to corticotropic action of the hormone and is not associated with blood levels of glucocorticoids.