Stress in early ontogenesis and reactivity of hypothalamo-pituitary-adrenal system in adult rats.

Various stressors (laparotomy, cold or amphetamine injection) applied during the last third of pregnancy resulted in an increase of corticosterone level in mothers and a decrease of the response to emotional stressor (restriction) in their adult offspring. The same results were found after a single injection of hydrocortisone to the mothers on the 18th day of pregnancy. Adrenalectomy in mothers performed one month before the pregnancy prevented such effects. The stress (daily injections of saline s.c.) applied between 7th and 9th day of postnatal life resulted in increased corticosterone level in adult animals together with a decrease of their response to emotional stress (restriction) and, finally, in an increase of adrenocortical response to intracerebroventricular injection of noradrenaline. Similar injections of hydrocortisone between 7th and 9th day were without any effect. It is concluded that the effect of stress during the last third of pregnancy on HPAS of adult offspring may be mediated by the activation of maternal adrenal cortex. The modification of HPAS function resulting from the action of stressors during early postnatal life may be due to a relative insufficiency of corticosteroid release during the postnatal stimulation rather than to an increase of their absolute level.