Dissociation of conditioned and unconditioned factors in the running-induced feeding suppression

In adult rats, running wheel introduction induces a 7 to 10 day feeding suppression, either due to a learned conditioned taste avoidance or to the direct unconditioned effects of wheel running. The three experiments investigated the effects of wheel introduction on familiar (rat chow) and novel (24% sucrose solution) food consumption (Experiment 1), and then explored how alternate-day wheel access affected sucrose consumption when it was novel (Experiment 2) or familiar (Experiment 3). When paired with wheel introduction the consumption of a novel sucrose solution was completely suppressed for an extended period, whether the rats had continuous or alternate-day wheel access. In contrast, familiar food consumption was suppressed, for a limited period, only on wheel days. When rats were pre-exposed to the sucrose, consumption was suppressed only on wheel days. The results suggest that in addition to the direct unconditioned effects of wheel running on feeding, learning factors may influence the feeding suppression observed and thus wheel introduction supports a learned conditioned taste avoidance.