EFFECTS OF BUPRENORPHINE ON MOTILITY IN CHRONICALLY MORPHINE TREATED RATS

The effects of buprenorphine (0.0 1 -0.1 mg/kg) on the activity of non dependent and morphine dependent rats (a 20 mg/kg dose for 28 days) we re determined. In naive animals buprenorphine exhibited both depressiv e and stimulatory actions upon the motility of rats, as repeatedly des cribed for morphine. When buprenorphine was administered to rats chron ically treated with morphine, the depressive effect disappeared (cross -tolerance to the inhibitory action); on the contrary the excitatory e ffect was enhanced (cross-sensitization). The results are discussed in terms of cross-sensitization to the excitatory effects in morphine de pendent animals as predictor of morphine-like addictive properties in humans.