Objective: To investigate the effects of clobenpropit and histidine on reinstatement of morphine-induced conditioned place preference (CPP) in rats.
Methods: The persistence, extinction and reinstatement of morphine-induced CPP were established.In clobenpropit group three different doses of clobenpropit (2, 5 and 10 microg/rat, i.c.v.) were administered 15 min after morphine (1 mg/kg, i.p.) was injected. In histidine group histidine (100, 200, 500 mg/kg) was given 1 h prior to morphine treatment (1 mg/kg i.p).
Result: The CPP was reinstated by priming injection of 1 mg/kg morphine. Clobenpropit (5, 10 microg/rat) significantly inhabited the reinstatement by a priming dose of morphine-induced CPP compared with the morphine control group; histidine (100, 200, 500 mg/kg) significantly inhibited the reinstatement in a dose-dependent manner.
Conclusion: Clobenpropit and histidine inhibit the revival of morphine-induced CPP in a dose dependent manner, indicating that endogenous histamine may inhibit relapse of morphine to some extent.