The sense of taste in the upper gastrointestinal tract.

Digestion and the absorption of food and nutrients have been considered the only functions of the gastrointestinal (GI) tract. However, recent studies suggest that taste cells in the oral cavity and taste-like cells in the GI tract share many common characteristics (taste receptors and transduction signaling). Over the last two decades, it has been revealed that the GI tract is a chemosensory organ that transfers nutrient information via GI hormone secretion (glucagon-like peptide-1, Peptide YY, oxyntomodulin, glucose-dependent insulinotropic polypeptide and others) and the activation of abdominal vagus afferents. In addition, the information relayed via the abdominal vagus nerve plays an important role in autonomic reflexes. This information, both humoral and neural, contributes to the maintenance of homeostasis (digestion, absorption, metabolism and food intake) in the body. In this review, we provide a brief overview of the following: GI chemosensory molecules, their distribution, the effect of nutrients on GI hormone secretion and the activation of vagus afferent nerves. We also focus on the possibility of clinical applications that control abdominal vagus activity.