Behavioural specificity of chlordiazepoxide-produced StD

Low doses of benzodiazepines produce state-dependence (StD) of food-rewarded lever pressing in rats, and it has been hypothesized that the changes of memory states that can thus be studied constitute the mechanism whereby benzodiazepines cause their characteristic psychopharmacological actions such as anxiolysis, apparent memory loss and dependence. Non-benzodiazepine CNS agents such as NMDA antagonists also produce StD in this procedure, suggesting that the StD hypothesis of psychopharmacological drug action can be expanded to include agents other than benzodiazepines. For this expansion to be possible, however, it must be shown that the StD mechanism operates in a specific manner. The present experiments examined whether varying the extent of food deprivation affects any of a number of quantitative features of chlordiazepoxide (CDP)-induced StD of food-rewarded lever pressing in rats. The data indicate that the CDP doses required to generate StD in both drug-to-saline and dose-to-dose transfer tests, are considerably lower in relatively sated as opposed to more deprived animals; little or no difference was found in tests assaying saline-to-drug transfer. The data add behavioural to available pharmacological evidence supporting the hypothesis that changes of memory state constitute the mechanism whereby CNS agents such as benzodiazepines and NMDA antagonists cause their characteristic psychopharmacological actions. Some directions for future research are identified to explore further the pharmacological and behavioural specificity of drug-produced StD.