Abstract
Taste is essential in controlling food intake: taste palatability is one of the most important factors that facilitate food intake and modulate the homeostatic control of feeding. The present article describes the mechanism of this phenomenon in terms of interplay of brain substances such as endogenous opioids, cannabinoids, dopamine and orexin. Taste information is sent to the reward system and feeding center via the prefrontal cortex in rodents and the orbitofrontal cortex in primates. The amygdala, which receives taste inputs, also influences reward and feeding. In terms of neuroactive substances, palatability is closely related to benzodiazepine derivatives, β-endorphin and cannabinoids, which facilitate consumption of food and fluid. The reward system contains the ventral tegmental area, nucleus accumbens and ventral pallidum and finally sends information to the lateral hypothalamic area, the feeding center. The dopaminergic system originating from the ventral tegmental area mediates the motivation to consume palatable food. To elucidate the brain mechanisms of the palatability-induced ingestion, we focused on the role of orexin, a hypothalamic neuropeptide, on the basis of recent findings that rats after intracerebral injection of orexin enhanced food intake accompanying the “binge eating pattern” and orexin-knockout mice decreased intake of palatable sucrose solution. Thus, palatability is one of the factors that regulates food and fluid intake and contributes to overconsumption in turn contributing to obesity.
