SENSITIZATION OF STRESS-INDUCED FEEDING IN RATS REPEATEDLY EXPOSED TOBRIEF RESTRAINT - THE ROLE OF CORTICOSTERONE

Groups of male Wistar rats lived in cages capable of monitoring feedin g and drinking continuously at 0.1-s intervals, 24 h per day. Intact a nimals were subjected to 20 min of restraint stress or to brief handli ng (Brief Pick-Up), daily or every third day, 6 h after the beginning of the 12-h light period. In both studies, food-intake increased in th e first hour after restraint, peaking between 15 and 45 min. Smaller i ncreases were seen following Brief Pick-Up. More interestingly, the am ount of food eaten increased across test sessions, indicating sensitiz ation of the response to stress. Drinking also increased following str ess, occurring before feeding and diminishing after the first 15 min. In adrenalectomized animals implanted with slow-release pellets to rep lace basal diurnal levels of corticosterone (ADX animals), sensitizati on of the feeding response to restraint stress developed across test s essions, although in these animals, the acute increase in food-intake following restraint stress was attenuated. ADX animals subjected only to Brief Pick-Up showed no increases in food-intake. Daily injections of 3.0 mg/kg corticosterone given to such ADX animals were unable to m imic the effects of restraint on either food-intake or drinking, nor d id they augment the effects of restraint in ADX animals. We conclude t hat sensitization to the effects of brief restraint stress on food-int ake can occur independently of a stress-induced rise in plasma cortico sterone.