Pavlovian counterconditioning is unchanged by chlordiazepoxide or by septal lesions

Two experiments were performed to test whether the minor tranquillizer chlordiaz-epoxide or septal lesions could interfere with Pavlovian counterconditioning. Rats were first trained to bar-press for food on a random interval schedule on which was superimposed the presentation of a light which predicted delivery of a shock. This training continued until all animals were showing stable suppression of responding to the light. Separate groups were then presented, while the manipulandum was retracted from the box, with either a shock paired with the delivery of food or shock and food delivery in a random relationship with one another. This type of intrusion period alternated with the presentation of the light and shock. Pavlovian counterconditioning developed, as shown by progressively less response suppression in the paired groups compared to the random groups. This Pavlovian counterconditioning was in no way reduced by either chlordiazepoxide (5 mg/kg) or by medial or lateral septal lesions. It is argued that these results rule out Pavlovian counterconditioning as a process which is affected by minor tranquillizers or by septal lesions when they interfere with the behavioural tolerance observed after partial punishment or partial reward schedules.