Properties of pentazocine as a discriminative stimulus in the squirrel monkey

JM White and SG Holtzman

Squirrel monkeys were trained to discriminate i.m. injections of pentazocine (3.0 mg/kg) from vehicle. Stimulus control was considered to have been established when the monkeys reliably completed at least 22 of the 25 trials (i.e. 88%) on the appropriate lever in both pentazocine and vehicle sessions. In cross-generalization tests, two groups of drugs were shown to produce pentazocine-like discriminative effects: 1) the pure opiate agonists morphine, levorphanol and levomethorphan and 2) cyclazocine, phencyclidine and dextrorphan, drugs previously shown to have common discriminative effects. In addition, l- pentazocine proved to be about twice as potent as the racemic mixture. Butorphanol, SKF 10,047 and dextromethorphan produced pentazocine- appropriate responding in 80% of the trials, whereas ketocyclazocine, ethylketocyclazocine and nalbuphine produced less than 50% pentazocine- appropriate responding. Four nonopioid drugs from a variety of pharmacologic classes (apomorphine, d-amphetamine, secobarbital and mescaline) failed to show any discriminative properties in common with pentazocine. In antagonism studies, naltrexone completely blocked the discriminative effects of pentazocine, whereas haloperidol produced only a partial blockade. The discriminative effects of l-pentazocine and levorphanol could also be antagonized by naltrexone, but those of dextrorphan could not. The results suggest the pentazocine has both a morphine-like component of action and a component shared with the nonmorphine-like opioids.

Volume 223, Issue 2, pp. 396-401, 11/01/1982
Copyright © 1982 by American Society for Pharmacology and Experimental Therapeutics

This article has been cited by other articles:

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