Rats were trained to lever press for sucrose on a random interval (RI) 64-s schedule. During a 55 min session there were four 3 min "intrusion periods" signalled by a flashing house-light. In experiment 1 there were two groups matched for baseline response rate. During the intrusion periods one group received response-independent footshock on an independent RI64 schedule; the other group received responsecontingent shock on this schedule. Shock intensity was varied for each rat to match degree of response suppression between the two groups. Chlordiazepoxide HCl (CDP) in doses 0.5-5 mg/kg alleviated response suppression equally in both groups. Experiment II followed the same procedure, except that all animals had the same shock intensity, producing greater response suppression in the response-contingent shock groups. CDP alleviated response suppression more in the response-contingent shock groups, significantly so at 5 mg/kg, nonsignificantly at 1 mg/kg. These results suggest that previous reports that CDP differentially alleviates the response suppression produced by response-contingent shock are an artefact of rate dependency.
- Conditioned suppression