Pituitary-adrenal axis and behavioural responses of maternally deprived juvenile rats to the open field

Adult rats submitted to maternal deprivation (DEP) on post-natal day (pnd) 11 show smaller corticosterone (CORT) response to a saline injection than n on-deprived (NDEP) rats, mainly at 30 days of age. In the present study we sought to investigate the pituitary-adrenal axis response of 30-day-old DEP rats to a 5-min open-held session, with lights and sound on. Hormone level s were assessed immediately or 20 min after the end of the stress, and were compared to basal levels. The immediate ACTH response of DEP females was t he highest; this difference was no longer observed at 20 min, but hormone l evels were still. higher than basal. Both males and females showed an augme nted CORT secretion immediately after the open held session, although only the response of NDEP females was higher than that of male counterparts. Mor eover, DEP females showed a lower CORT response than their NDEP counterpart s immediately after the stress. The CORT stress response remained equally e levated in males and females at the 20-min time point. Finally, DEP animals , regardless of the gender, ambulated more in the centre of the open field and displayed less grooming behaviour than NDEP pups, suggesting that DEP r ats are less emotional than NDEP animals. (C) 2000 Elsevier Science B.V. Al l rights reserved.