Effect Of Scopolamine On Reinstatement Of Conditioned Place Preference In Morphine Dependent-rats

Objective: To investigate the effects of different dose scopolamine on reinstatement of conditioned place preference (CPP) and the expression of phosphorylation of cyclic AMP response element binding protein( p-CREB) and immediately early gene c-fos in nucleus accumbens (NAc), amygdale (AMG), hippocampus (HIP)and prefrontal cortex (PFc) of morphine dependent -rats. Methods: Morphine was administered by subcutaneous injection at gradually increasing dose for 6 days((d1 SC 10mg/Kg,increasing 10mg/Kg every day, till d6 SC 60mg/Kg) to establish morphine conditioned place preference (CPP).CPP was measured in day 7. From day 8, the rats were administered saline instead of morphine to induce CPP extinction for 10 days and CPP was measured again. The rats were given a single priming injection of morphine 4mg/kg to restate the morphine CPP. Some rats were treated by ip scopolamine (1mg/kg, 2mg/kg, 3mg/kg) and naloxone (1mg/kg) prior to priming injection of morphine half an hour. The rats were examine the time spent on the drug paired side next day. The effect of scopolamine on the expression of p-CREB and c-fos in different brain sites of rats in the reoccurrence of CPP model, including NAc, AMG, HIP and PFc was measured by immunohistochemical method. Results: 1.After priming injection of morphine 4 mg/kg, the time spent on the drug paired side was significantly reduced because of the treatment with scopolamine, compared with morphine group (P<0.05).2.The expression of p-CREB and c-Fos in morphine -dependent rats were significantly increased in NAc, AMG, HIP and PFc as compared with control group. The expression of p-CREB and c-fos in scopolamine treated rats were significantly decreased in different brain sites, including NAC, AMG, HIP and PFc, as compared with morphine group. .Conclusion: 1.scopolamine can block on reoccurrence behavior of CPP which is induced by priming injection of morphine in morphine-dependent rats.2.Scopolamine may effectively attenuate the expression of p-CREB and c-fos in different brain sites in the model of reoccurrence of CPP in morphine dependent-rats, including NAc, AMG, HIP, and PFc.