Strain differences in the effects of chlorpromazine and chlordiazepoxide upon active and passive avoidance in mice

Summary

Four inbred strains of mice were compared on an active and a passive avoidance task in a two-compartment cage. Active mice were trained to cross frequently between compartments to avoid shock; passive mice were shocked for crossing. Yoked controls in both procedures received shocks at the same time as experimentals. Strains learning the active task well did poorly in the passive task; strains poor in active learning were superior on the passive task. The results support the view that strain differences in avoidance learning are more related to variations in strength of a kinetic drive than to strength of fear. Chlordiazepoxide affected crossings similarly in actively and passively trained Ss; chlorpromazine reduced crossings in actively trained and increased crossings in passively trained Ss. This result is consistent with dual motivational systems differentially susceptible to alteration by administration of drugs. Chlordiazepoxide acts primarily upon kinetic drive; chlorpromazine upon fear.