Effects of maternal separation during early postnatal development on male sexual behavior and female reproductive function

The endocrine response to stress is an important homoeostatic mechanism, an d the secretion of glucocorticoids from the adrenal cortex is a central fea ture of this response. During early postnatal development, the neonatal rat displays a reduced hypothalamic-pituitary-adrenal (HPA) response to stress . This early period has been termed the 'stress hyporesponsive period' (SHR P). Maternal separation (Sep) of neonates from their mothers during early p ostnatal development alters the HPA response to stress. In this study, we r eport the effects of Sep during the SHRP. Female rats were time mated and r andomly divided into control or Sep groups before birth. The Sep litters we re removed from the mothers during the dark cycle for 6 h per day from post natal day (PND) 2 to 10. On PND 28, the pups from both groups were weighed, the anogenital distance (AGD) was measured and the animals weaned. At 40 d ays of age, male and female animals from both groups were tested for open-f ield activity. As the animals matured, vaginal opening and estrous cycles w ere measured in females, and males were tested for male sexual behavior at adulthood. Basal, stress, and stress recovery serum corticosterone levels w ere measured from control and Sep male and female animals. Open-field activ ity was not significantly different between control or Sep male or female a nimals. Sep did not affect either vaginal opening or estrous cycles in fema le animals. Corticosterone secretion in response to stress was similar in c ontrol and Sep males and females; however, the recovery levels were signifi cantly higher in Sep females than in Sep males or female control values. Tn male sexual behavior tests, Sep males had significantly longer mount laten cies (time to the first mount), longer intromission latencies (time to the first intromission) and a significant reduction in the percent of animals e jaculating versus control values (controls 84 and Sep 50%). Therefore, Sep males as adults displayed altered reproductive behavior, whereas their stre ss recovery levels of corticosterone returned to near basal levels in a sim ilar fashion to that observed for control non-handled males. In contrast, f emales displayed normal reproductive physiology, while their recovery level s of corticosterone remained high, unlike that observed with control female s. Thus, significant gender differences in response to Sep (during the dark phase of the circadian cycle) were observed in the paradigm used in the pr esent study. (C) 2001 Elsevier Science B.V. All rights reserved.