DIFFERENTIAL-EFFECTS OF VENTRAL STRIATAL LESIONS ON THE CONDITIONED PLACE PREFERENCE INDUCED BY MORPHINE OR AMPHETAMINE

The present experiment examined the role of the ventral striatum in th e rewarding effect of morphine and amphetamine by testing whether lesi ons of cell bodies within this region disrupt the development of a con ditioned place preference to either drug. Bilateral, N-methyl-D-aspart ate- or kainic acid-induced lesions of the ventral striatum block a co nditioned place preference to amphetamine (1.5 mg/kg x 3 pairings) but not to morphine (2 mg/kg x 3 pairings). Because both lesions spared a nterior portions of the ventral striatum, we examined the effect of la rger or more selective ventral striatal lesions on a conditioned place preference induced by morphine. Destruction of the entire ventral str iatum reduced, but did not eliminate, a conditioned place preference t o morphine, whereas selective lesions of the anterior ventral striatum were ineffective.These results indicate that the ventral striatum is not critically involved in morphine's rewarding effect and support the suggestion that the rewarding effects of opiates and stimulants do no t involve identical neural substrates.