The effects of chlordiazepoxide and Ro 15-1788 on preference for punished and unpunished response alternatives

Male, food-restricted, hooded rats were trained to respond on a two-component multiple schedule. Reinforcement density was several times higher in one component than in the other component, but responses were intermittently punished with shock in the richer reinforcement component (conflict situation). Half of the rats controlled which component was operating (Preference Group), while half did not (Yoked Group). The effects of the benzodiazepine chlordiazepoxide (CDZ; 1, 3 and 10 mg/kg; i.p.) on component preference was measured. Also examined were the effects of CDZ on food-reinforced responding that was either punished (in the conflict situation) or not punished. CDZ increased both time spent in a punished component and response rate in that component. These findings are consistent with similar findings from concurrent schedules and for the first time demonstrate this relationship in a paradigm that does not invariably generate a positive correlation between response rate and preference. Response rates were also increased in the unpunished response alternative, but to a lesser degree than in the conflict situation. These effects of CDZ were at least partially mediated by the benzodiazepine receptor given that CDZ's effects were diminished by Ro 15-1788 (10 mg/kg; i.p.), a benzodiazepine antagonist. Further, CDZ's effects on response rates and preference were not mimicked by removing the shock contingency in the conflict situation. This supports the argument that CDZ was not acting via analgesic actions.