The effect of phase-shift on the passive avoidance response in rats and the modifying action of chlordiazepoxide.

1 In rats trained to a 12 h light-12 h dark cycle, advancing the phase by 6 h produced a resynchronization of the 24 h variation in passive avoidance response (PAR) which was completed after 10 days.2 The attainment of the new steady state was preceded by a period of disruption which was greatest 5 days after phase-shift.3 The presence of chlordiazepoxide (62.5-500 mug/ml) in the drinking water during the days after phase-shift produced a dose-dependent lessening of the disruptive effect of phase-shift, and a more rapid adaptation to the new light-dark cycle.