Bidirectional operant conditioning of heart rate in rats with sucrose reward

Abstract

Sucrose was used to reinforce heart rate (HR) increases in one group of unrestrained rats and to reinforce decreases in another. A third group received noncontingent sucrose presentations, and a fourth was presented with an empty dipper. After 10 conditioning sessions HR, as measured by changes in tonic levels, was significantly greater in the Fast group than in the Noncontingent group, which in turn maintained significantly higher levels than the Slow group. There was no difference between the Noncontingent and No-sucrose groups. Behavioral observations indicated that the Fast animals increased the percentage of time spent in such high-HR categories as rearing and walking; however, there were no corresponding systematic decreases in the Slow animals. Moreover, the Fast and Slow groups differed significantly with regard to the HRs associated with five behavioral categories. The overall pattern of results suggests that some degree of cardiospecific effect may have been exerted by the operant contingencies.