The partial reinforcement extinction effect: Influence of chlordiazepoxide in septal lesioned rats

Rats sustained electrolytic lesions either in the medial septal (MS) or lateral septal (LS) area or they were sham-operated. They were tested in the straight alley with food reward on either continuous (CRF) or partial (PRF) reinforcement at one trial a day and were injected with either 5 mg/kg chlordiazepoxide HCl (CDP) or with saline before the daily trial throughout acquisition and extinction. The effects of the drug on resistance to extinction interacted with those of the LS lesion in ways which were consistent with the hypothesis that CDP acts via the lateral septal area if it is injected during acquisition on a PRF schedule. MS lesions produced only small changes in the effects of CDP. In general, CDP acted to reverse the effects produced by each lesion: Under those conditions in which MS lesions produced faster running speeds, CDP caused the lesioned animals to run slower; and under those conditions in which LS lesions produced slower running speeds, CDP caused the lesioned animals to run faster.