Abstract

Background: In the present study, the effects of water-alcohol extract of Papaver rhoeas on the expression and acquisition of morphine-induced Conditioned Place Preference (CPP) in male N-MARI mice (20-25 g) were investigated. Methods: In a pilot study, different doses of morphine or the extract were administered to the animals to indicate whether the drugs could induce place preference in particular apparatus. In the second part of the experiment, the animals received different doses of extract 30 min before each morphine injection (acquisition) or 30 min before beginning of the test (expression). Results: Subcutaneous (SC) administration of morphine (1, 10 and 20 mg/kg) produced place preference. On the other hand, intraperitoneal (IP) administration of the plant extract (25, 50 and 100 mg/kg) did not show any effect. Injection of extract (25, 50 and 100 mg/kg, IP) 30 min before the morphine administration decreased the acquisition of morphine CPP. Administration of the plant extract (25, 50 and 100 mg/kg, IP) 30 min before the test increased the expression of morphine-induced CPP. Conclusion: It could be concluded that the extract of Papaver rhoeas reduced the acquisition, but did not influence the expression of morphine-induced conditioned place preference in mice.