Effects of Papaver rhoeas Extract on the Tolerance Development to Analgesic Effects of Morphine in Mice

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.