Discriminative stimulus properties of the isomers of pentobarbital and secobarbital in pigeons

GR Wenger

Department of Pharmacology and Interdisciplinary Toxicology, University of Arkansas for Medical Sciences, Little Rock.

To date there have been no reports on the discriminative stimulus properties of barbiturate isomers in laboratory animals or man in which the individual isomers were used in the development of the discrimination. To determine what stereospecificity might exist for the stimulus properties of barbiturate isomers, one group of pigeons was trained to discriminate 5 mg/kg of (S)-(-)-pentobarbital from saline and another group was trained to discriminate 8 mg/kg of (R)-(+)- pentobarbital from saline. After responding had stabilized, dose- response curves were determined in both groups for (S)-(-)- pentobarbital (0.3-10 mg/kg), (R)-(+)-pentobarbital (1-17.5 mg/kg), (S)- (-)-secobarbital (0.3-10 mg/kg), (R)-(+)-secobarbital (1-17.5 mg/kg), racemic Na.pentobarbital (1-17.5 mg/kg) and racemic Na.secobarbital (1- 17.5 mg/kg). In both groups of pigeons, both isomers of pentobarbital and secobarbital, as well as racemic pentobarbital and racemic secobarbital, showed complete generalization to the training stimulus. For both pentobarbital and secobarbital, the S-(-) isomers showed generalization to the training drug at lower doses than the corresponding R-(+) isomers. No differences were observed in the dose- response curves for the racemic mixtures as a function of the training drug. Thus, no stereoselective differences other than potency could be demonstrated for the stimulus properties of the isomers of pentobarbital and secobarbital.

Volume 245, Issue 2, pp. 389-393, 05/01/1988
Copyright © 1988 by American Society for Pharmacology and Experimental Therapeutics