Effects of chlordiazepoxide on passive avoidance responses in rats

The effect of chlordiazepoxide on the retention of a passive avoidance response was determined in rats. Chlordiazepoxide or saline was given before testing in a two compartment passive avoidance response (PAR) apparatus or in an open field, and again after 48 and 72 h.The PAR was usually depressed by chlordiazepoxide (CDP) given during acquisition, and it remained present after 48 and 72 h. Treatment with chlordiazepoxide before the second and third testing abolished the depression of PAR. CDP had most effect on the acquired PAR.Shock treatment resulted in an increase in defecation and urination and a decrease in ambulation and rearing in the PAR apparatus as well as in the open field. These effects were reduced by CDP, irrespective of drug-state changes. A clear-cut reduction in defecation and urination under CDP in well-habituated home cages was also seen. The depressant effect of CDP upon the PAR is discussed in relation to the drug's inhibitory action upon the hippocampal theta activity.