Abstract

Previous studies have shown that the extract of Papaver rhoeas reduces morphine dependence, locomotor activity and reward. In present study, the effects of hydro-alcohol extract of Papaver Rhoeas on the tolerance to analgesic effects of morphine in mice have been investigated using tail flick method. Subcutaneous (s.c.) administration of morphine (1, 2, 5 and 10 mg/kg) induced analgesia. However, intrapretoneal administration of the hydro-alcohol extract of Papaver rhoeas (25, 50 and 100 mg/kg) had not an effects on analgesia. Reduction of analgesic in mice pretreated with morphine (50 mg/kg, twice daily; for 3 days), alone, indicated that tolerance has been developed. Hydro-alcohol extract of Papaver rhoeas (25, 50 and 100 mg/kg, i.p.) administration, 30 min before each of three daily doses of morphine, attenuated the morphine tolerance dose-independently, indicating that administration of the extract reduces morphine tolerance in mice.