THE EFFECTS OF l-THP ON MORPHINE-INDUCED DISCRIMINATION

Objective: To explore the effects o f l-THP (l-tetrahydropalmatine) on drugs with psychic dependence producing poten tial. Methods:The rats were trained to discriminate morphine (2.50 mg·kg -1) from saline under fixed-ratio schedule and after the dis crimination established, morphine of different doses(0.31、0.63、1.25、2.50 mg·kg -1) was given to substitute for the training dose. Then, the rats we re administered with DA receptor antagonists Sch23390, raclopride and l-THP (1. 25、2.50、5.00 mg·kg -1), respectively to antagonize the effect. Results:The rats acquired morphine discrimination at the dose of 2 .50 mg·kg -1 and the effect was antagonized by Sch23390, raclopride a nd l -THP, and l-THP could dose-dependently antagonize the effects of morphine. Conclusion:The rats can steadily discriminate morphine from salin e and DA receptors are involved in this effect. The effect of l-THP on the discr iminative stimulus suggests that l-THP can inhibit the psychic dependence of mor phine.