EFFECTS OF CCK-8 ON THE REINSTATEMENT OF MORPHINE-INDUCED CPP AND EXPRESSION OF BEHAVIORAL SENSITIZATION IN RATS

摘要

Cholecystokinin octapeptide (CCK-8), a neuro-peptide, plays an important role in morphine dependence and several addictive behaviors. We have previously reported that CCK-8 attenuates the acquisition of morphine-induced conditioned place preference (CPP), but the possible functions of CCK-8 on drug relapse remain unclear. Here we evaluated the effects of CCK-8 on the reinstatement of extinguished morphine-induced CPP and behavioral sen-sitization. A single injection of 0.1 and 1 jig CCK-8 (i.c.v.) significantly attenuated both drug- (morphine) and stress-(foot shock) primed reinstatement of CPP and reduced the escalated locomotor activity in reinstatement tests. Additionally, CCK-8 blocked the expression of morphine-induced behavioral sensitization. However, administration of CCK-8 (0.01, 0.1 and 1 ug) alone to morphine-pretreated rats could not trigger reinstatement of CPP and had no significant effect on threshold sensitivity to foot shock. In conclusion, our study identifies a distinct inhibitory effect of CCK-8 on the reinstatement of drug-seeking behavior and provides a potential application to the medication of drug relapse.