Chlordiazepoxide increases the force of two topographically distinct operant responses in rats

By using operant conditioning techniques one group of 8 rats was trained to reach through a hole in the wall of an operant chamber, and to exert downward responses on a force-sensing circular disk. Eight other rats learned to reach through the hole and grasp and pull toward them a wire bail attached to a force transducer. Both behaviors were maintained on a fixed ratio 20 schedule of water reinforcement. The effects of chlordiazepoxide (CDP, 2.5, 5.0, 10.0 mg/kg) on response force and rate were assessed for both groups. CDP significantly increased response force in a dose-related manner in both groups; regardless of topography, response rate was little affected by the 2.5- and 5.0 mg/kg doses but was decreased by the highest dose. Results were discussed in terms of CDP's antipunishment and neuromuscular effects.