OPIATE AGONIST-INDUCED CHANGES IN BEHAVIORAL SENSITIVITY TO CLONIDINEARE OBSERVED IN PERINATALLY MALNOURISHED RATS EXPOSED TO CHRONIC STRESS

Sensitivity of alpha(2)-adrenoceptors following repeated immobilizatio n sessions plus morphine (MOR) or beta-endorphin (BETA) was assayed by examining clonidine (CLO)-induced hypoactivity in adult malnourished rats at perinatal age. As previously described, chronic restraint did not attenuate the hypoactivity elicited by CLO in malnourished rats, a lthough chronic restraint did have such an effect on motor activity in control animals. MOR and BETA administration prior to each restraint session induced subsensitivity of alpha(2)-adrenoceptors in malnourish ed rats as determined by a blunted response to clonidine challenge. An injection of naloxone (NAL) prior to BETA before each stress session fully antagonized the subsensitivity to clonidine observed in malnouri shed animals. A possible deficiency in the functional role of the opia te system in the process of adaptation to chronic stress in perinatal malnourished rats is suggested. (C) 1998 Elsevier Science Inc.