SOCIAL DEPRIVATION ENHANCES THE VULNERABILITY OF MALE WISTAR RATS TO STRESSOR AND AMPHETAMINE-INDUCED BEHAVIORAL SENSITIZATION

The aim of the present study was to assess the influence of experienti al factors on the vulnerability of rats to develop amphetamine (AMPH)- and stressor-induced behavioral sensitization. Young male Wistar rats with previous social experience were isolated from their peers for 2 weeks. 1) The effect of this short-lasting social deprivation were: a) a reduced tendency to explore a fearful environment; b) a prolonged e xploratory activity in response to a novel but little fearful environm ent; and c) a dose-dependent increase in the psychomotor stimulation i nduced by systemic AMPH injection. 2) After repeated AMPH injections ( injection every other day for 10 days), isolated rats exhibited behavi oral sensitization at lower doses (0.5 and 0.75 mg/kg) than those requ ired for group-housed rats (1 mg/kg). 3) After being submitted to a re peated stressor (3, 7 or 14 footshock sessions, with 2 days between se ssions), the isolated rats exhibited a greater increase in the behavio ral responsivity to a subsequent AMPH challenge (1 mg/kg) than did the group-housed rats regardless of the number of stress sessions. In con clusion, these results suggest that experiential factors such as priva tion of contact with peers (social isolation) may make rats more vulne rable to the long-term repercussions of chronic environmental and phar macological challenges.