AGE AND STRESS HISTORY EFFECTS ON SPATIAL PERFORMANCE IN A SWIM TASK IN FISCHER-344 RATS

This study determined whether prior habituation to water immersion wou ld ameliorate age-related deficits in learning and memory in a swim ta sk. Aged (22 months) and young adult (3 months) rats were immersed in water (30 degrees C) for 15 min on each of 28 consecutive days before training in the swim task. Additional groups of age-matched animals se rved as handled controls. Training on a spatial discrimination version of the water task was conducted over 5 days with two trials per day ( 1-h intertrial interval). A probe trial was substituted for the last t rial on the fifth day to assess the rats' use of spatial information. Three days later, rats received cue discrimination training to find a visible platform. In the spatial task, prior habituation to water imme rsion ameliorated deficits in acquisition within each day (i.e., at a 1-h intertrial interval) but not across days (at 24 h). The results ob tained with the 24-h interval confirm the rapid forgetting characteris tic of aged rats in many tasks. The stress-habituation procedures redu ced age-related deficits seen on the probe trial and on cue discrimina tion training. These findings indicate that several aspects of age-rel ated impairments in the swim task, often attributed to primary age-rel ated deficits in learning and memory processes per se, may instead be secondary to age-related differences in stress responses to water imme rsion. (C) 1996 Academic Press, Inc.