The prevalance of opioid addiction is releativly high in Iran. Since the mechanism (s) of opioid addiction are not clear, this social problem still remains unresolved. In the present study, the effects of water-alcohol extract of Papaver rhoeas on the acquisition and expression of morphine withdrawal in morphine-dependent N-MARI mice (20-25 g) were investigated. The animals became dependent to morphine and the extract of the Papaver rhoeas was administered during and after induction of morphine dependence. Then, withdrawal syndroms were tested with naloxone (4 mg/kg) injection. Results showed that administration of naloxone after four days morphine treatment (12.5, 25 and 50 mg/kg), induced diarrhea and also increased the number of jumping in animals. The increase was significant for a dose of 50 mg/kg of morphine. On the other hand, administration of the plant extract (25, 50 and 100 mg/kg) did not induce any changes in the feaces or number of jumping behaviour in the animals. Injection of the same extract (25, 50 and 100 mg/kg) 30 min before morphine (50 mg/kg) administration, caused an increase in number of jumping but reduced the diarrhea in animals. Injection of the plant extract (25, 50 and 100 mg/kg) on the test day, 30 min before naloxone administration also decreased the number of jumping and diarrhea in morphine-dependent animals. It could be concluded that the extract of Papaver rhoeas can amilorates the withdrawal syndrom in morphine-dependent mice. Therefore, the extract might be useful for treatment of withdrawal signs in opioid addicts.

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.