Involvement of the mesolimbic system in palatability-induced ingestion.

The pleasantness of taste powerfully influences the preference for food and fluids. Particularly palatable tastes can lead to considerable overconsumption. Because palatable foods and fluids are potentially nutritive, animals are highly motivated to ingest them. The brain regions along the taste pathway and its anatomical interfacing with the brain reward system are thought to be involved in palatabilitydependent consumption (Kelley et al., 2002). However, the role of the mesolimbic system in the behavioral expression induced by taste pleasantness is still unclear. Our previous studies (Shimura et al., 2002) demonstrated that lesions of the ventral tegmental area (VTA), the origin of the mesolimbic dopamine system, selectively affected the consumption of highly palatable solutions in rats. To obtain further information concerning the mechanisms of the reward system for palatability-driven ingestion, we recorded single neuron activities from the mesolimbic system during the licking of water and taste solutions in freely behaving rats.