Effect of penehyclidine hydrochloride on the reinstatement of conditioned place preference in morphine dependent rats

Abstract

Objective To investigate the effect of penehyclidine hydrochloride (PHCD) on the reinstatement of conditioned place preference (CPP) in morphine dependent rats. Methods Forty male adult SD rats weighing 180-220 g were randomly divided into 5 groups (n = 8 each): group control (group C); group morphine (group M) and 3 PHCD groups (group P1-3 ). Morphine 10 mg/kg was injected subcutaneously once a day for 8 days to induce morphine CPP. The rats were then subjected to extinction of CPP for 10 days with normal saline (NS) instead of morphine. After the extinction, the rats were put into the drug-paired side of the box. A single priming dose of morphine 4 mg/kg was injected to reinstate the morphine CPP. In group P1-3 the rats received PHCD 0.5, 1.0 and 1.5 mg/kg intraperitoneally 30 min prior to priming dose of morphine, whereas in group C and M the rats received NS. The second day the rats underwent CPP test. Results Compared with group M, the time spent in the drug-paired side (grey area) was significantly shortened in group P1-3 (P ＜ 0.05 or 0.01 ).Compared with group P1 ,no significant change in the time spent in the drug-paired side (grey area) was found in group P2(P ＞ 0.05), but the time spent in the drug-paired side (grey area) was significantly shortened in group P3 ( P ＜ 0.05). Conclusion PHCD could significantly inhibit the reinstatement of CPP induced by priming dose of morphine in morphine dependent rats and it is related to the dose. Key words: Cholinergic antagonists; Morphine dependence