Resistance to extinction of an avoidance response in rats following the administration of chlordiazepoxide (Librium) or diazepam (Valium)

In a one-way avoidance task with rats, injections of Librium (chlordiazepoxide) following avoidance acquisition resulted in prolonged resistance-to-extinction of the avoidance response. This effect occurred regardless of whether the rats had had prior experience with Librium or whether they were naive with respect to the drug. The same results were found with the same task when low doses of Valium were used. However, at a higher dosage an extreme reaction of either no responding or a high number of responses to extinction occurred in the naive animals. The Librium and Valium effects were compared to similar effects obtained using ethanol and hashish resin. These results indicate that the novelty hypothesis as originally stated by Amit and Baum cannot be supported because experience with the drugs prior to avoidance training did not attenuate the drug effect on avoidance.Supported in part by a grant to the Center for Research on Drug Dependence given to Dr. Z. Amit and a RODA summer studentship given to D. Ziskind.