Effects of chlordiazepoxide on the self-regulated duration of lateral hypothalamic stimulation in rats.

Rats were exposed to a fixed-interval 60-s schedule under which responding was maintained by electrical stimulation of the lateral hypothalamus. The duration of stimulation was controlled by the duration of each lever press that initiated reinforcement. The effects of variation in current intensity and administration of several chlordiazepoxide (CDP) doses (2.5--20 mg/kg IP) were investigated. The duration of stimulation was inversely related to current intensity. Administration of CDP resulted in increases in response rate and the durations of reinforced and non-reinforced responses. CDP increased the response duration reliably more with non-reinforced responses than with responses that served to regulate the duration of stimulation. Thus CDP-induced increases in the duration of brain stimulation with the single lever self-regulation procedure may not be attributed to a specific effect of this compound on neural processes underlying reinforcement. The present results indicate the utility of intermittent schedules in establishing the specificity of drug effects on self-regulated duration of brain stimulation in the single-lever condition.