Tripelennamine fails to enhance the morphine-like stimulus effects of pentazocine.

The effects of tripelennamine alone and in combination with morphine or pentazocine were examined in pigeons trained to discriminate between morphine (5.6 mg/kg, IM) and saline under a fixed ratio 30 schedule of food presentation. Tripelennamine (0.3-10.0 mg/kg) produced only saline-appropriate responding and dose-related decreases in response rates. When administered alone, both morphine (0.3-10.0 mg/kg) and pentazocine (1.0-30.0 mg/kg) produced dose-related increases in morphine-appropriate responding and dose-related decreases in response rates. When tripelennamine (0.3, 1.0 mg/kg) was administered in combination with morphine, the morphine dose-effect curve was not altered. Additionally, when tripelennamine (0.3, 1.0, 1.7 mg/kg) was administered in combination with pentazocine, tripelennamine did not alter the extent to which pentazocine produced morphine-appropriate responding. There was some suggestion that tripelennamine attenuated the effects of high doses of pentazocine; however, this effect did not occur in all pigeons. These results suggest that tripelennamine does not enhance the morphine-like discriminative stimulus properties of pentazocine in the pigeon, as it does in the rat.