The effects of FG 7142 and RO 15-1788 on the release of punished responding produced by chlordiazepoxide and ethanol in the rat

Abstract

Previous results in our laboratory have shown that both chlordiazepoxide and ethanol will release punished responding in a rat operant conflict test using incremental shock. In the present study, a benzodiazepine antagonist and a benzodiazepine inverse agonist were used to explore the neurochemical basis for this behavioral action. N-methyl-β-carboline-3-carboxamide (FG 7142) at high doses (20 and 40 mg/kg) produced suppression of both punished and unpunished responding, and reversed the release of punished responding produced by both chlordiazepoxide and ethanol, but only at doses that produced an effect on its own. FG 7142 thus acted to oppose the actions of both ethanol and benzodiazepines but in an additive, not interactive, manner. In contrast, RO 15-1788 produced no changes when injected by itself in doses as high as 12 mg/kg and reversed chlordiazepoxide-induced but not ethanol-induced release of punished responding. RO 15-1788 also reversed the decrease in punished responding produced by FG 7142. Results suggest that ethanol does not interact directly with the benzodiazepine binding sites on the GABA/benzodiazepine ionophore complex to produce its anxiolytic action.