EFFECTS OF REARING CONDITION ON ACTIVITY-INDUCED WEIGHT

This study evaluated the effects of differential rearing conditions on a rat protocol for various human syndromes. Subjects were 26 male Spr ague-Dawley rats, 24 days old at the start of the experiment, matched according to weight, acid randomly assigned to an isolation- or group- reared (4 rats/cage) condition. At 60 days of age (273 +/- 13 g), subj ects were individually housed in cages allowing access to running whee ls. Weight loss was produced through voluntary exercise and restricted food access. Animals in the isolation-reared condition lost weight at a faster rate and had heavier relative thymus weights than those in t he group-reared condition. Animals in both conditions ran equivalent d istances and ate equivalent amounts of food. The data show that postwe aning rearing conditions impact the interpretation of behavioral and p hysiological outcomes of animal models. The results implicate a shift from maternal regulation of pup physiological and behavioral systems t o the broader social niche. (C) 1995 John Wiley & Sons, Inc.