Punishment modifies the effects of chlordiazepoxide and benzodiazepine receptors

Abstract

Littermate groups of male albino rats responded under a procedure which generated comparable rates of punished and nonpunished responding. Chlordiazepoxide (3.0–30.0 mg/kg, IP) increased punished responding but had no effect on nonpunished responding. Homogenate receptor binding studies with [ 3H]Ro 15-1788 indicated increased benzodiazepine receptor binding in the striatum of rats who received shock. Moreover, a third group of rats exposed to noncontingent shock showed greater increases than those whose responses had been punished, suggesting that predictability and control of shock may have attenuated the effects of the noxious stimulus. Increased binding seen in the cerebellum, however, was related to the punishing effects of the electric shock since it occured only in those animals receiving response-contingent shock. There were no changes in binding affinity in any of the brain regions tested. Site-specific alterations in benzodiazepine receptors following electric footshock are related to the contigencies under which the noxious stimuli are administered. Furthermore, changes in benzodiazepine receptor binding may underlie the differential effects of benzodiazepine agonists on punished and nonpunished responding.