DIFFERENTIAL-EFFECTS OF POSTINGESTIVE FEEDBACK ON THE REWARD VALUE OFSUCROSE AND LATERAL HYPOTHALAMIC-STIMULATION IN RATS

The effects of postingestive feedback on the value of intraoral sucros e and lateral hypothalamic (LH) stimulation were compared. Rats chose between a fixed LH stimulation train or a compound reward composed of the same stimulation train and an oral infusion of 1 M sucrose. The ra ts preferred the compound reward when postingestive feedback was reduc ed by opening a gastric cannula. However, when the cannula was closed, the compound was preferred only at the beginning of each session, and preference declined or reversed as consumption continued. A second ex periment showed that the reduction in preference caused by closing the gastric cannula was not due to a punishing effect of the gastrointest inal load. This study suggests that postingestive signals modulate gus tatory reward al a stage of processing before gustatory and brain stim ulation rewards are combined.