Isolation rearing prevents the reinforcing properties of amphetamine in a conditioned place preference paradigm

Social isolation has been demonstrated to alter individual reactivity to addictive drugs. The present experiments compared the effects of isolation rearing and socially rearing rats on the reinforcing properties of amphetamine. Male Lister hooded rats were housed from 21 days (weaning) either alone (isolation reared rats) or in groups of four rats per cage (socially reared rats). Six weeks later, the rats were tested for their sensitivity to d-amphetamine (1.5 and 5 mg/kg) using a conditioned place preference paradigm. The treatment quadrant was selected as that in which the rat spent least time during a preconditioning trial. After saline conditioning, the socially reared rats showed a significant (P < 0.05) aversion for the treatment quadrant relative to the opposite quadrant. Following amphetamine (1.5; 5 mg/kg) conditioning, socially reared rats spent significantly more time (P < 0.05) in the treatment quadrant relative to the opposite quadrant while isolation reared rats failed to display either the aversion effect of saline conditioning or amphetamine induced place preference. These results demonstrate isolation rearing prevents the reinforcing properties of amphetamine.