Effects of chlordiazepoxide on runway behaviours of C57Bl/6 mice under continuous or partial reinforcement

An earlier history of partial or continuous reinforcement produces differential behavioural effects during extinction in the runway, with an earlier partial reinforcement (PRF) leading to an increased resistance to extinction. This effect has been attributed to conditioned frustration or generalization-decrement processes. The actions of antianxiety drugs in this procedure are most easily interpreted as for reducing the emotional or aversive effects of nonreinforcement. In this study, C57Bl/6 mice were trained to asymptotic performance with food reinforcement on 50 or 100% of six trials in daily sessions. The anxiolytic benzodiazepine, chlordiazepoxide (15 mg/kg, intraperitoneally) or saline was administered before subsequent daily extinction sessions. Under saline, earlier PRF produced an increased resistance to extinction. Drug administration increased resistance to extinction, as measured by start, run and goal times, after either continuous or PRF. These findings are consistent with earlier findings of rats, but different from those obtained with chlordiazepoxide during extinction after operant training with either rats or mice. These findings can be interpreted in terms of frustration, anxiety or generalization-decrement theories of PRF.