BEHAVIORAL AND MORPHINE-ANTAGONIST EFFECTS OF THE OPTICAL ISOMERS OF PENTAZOCINE AND CYCLAZOCINE

¹ Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina

The effects of d-, l-and dl-cyclazocine and d-, l-and dl-pentazocine were determined on the rate of conditioned key pecking in the pigeon under a multiple fixed-ratio fixed-interval schedule of food presentation. At low doses both isomers of cyclazocine and pentazocine increased the rate of key pecking under the fixed-interval schedule. At higher doses both isomers of cyclazocine and pentazocine decreased the rate of responding under both schedule components. The l-isomers were more potent in decreasing the rate of responding. Both d-and l-cyclazocine blocked the rate-decreasing effects of morphine on schedule-controlled behavior, but l-cyclazocine was more than 30 times as potent as d-cyclazocine. Neither d-nor l-pentazocine blocked the rate-decreasing effects of morphine.