The GI tract relies on hormones and neurotransmitters to inte- grate signals arising in the lumen with whole-body homeostasis.
As an example, satiety in the brain is to a great extent induced by the presence of food in the gut. This process begins with ingestion of nutrients that stimulate sensory cells in the intestinal epithelium that modulate food intake via the release of speci c chemical messengers.
GI hormones and neurotransmitters are intimately involved with every aspect of the diges- tive process, including ingestion and absorption of nutrients, so it is not surprising that these transmitters are essential for life.
In this chapter, the critical role of the regulatory trans- mitters in GI function is analyzed by covering the following aspects: their synthesis and secretion from sensory epithelial cells, how food or other GI luminal factors trigger their release, the most representative members, and their importance in the context of disease.