Fig. 6.
Appetite signals in the gastrointestinal−brain system. NPY neuropeptide Y, AgRP agouti-related protein, MSH melanocyte-stimulating hormone, POMC proopiomelanocortin, NTS nucleus tractus solitaries, ARC arcuate nucleus, PVN paraventricular nucleus, LHA lateral hypothalamic area, CCK cholescystokinin, GLP-1 glucagon-like peptide 1. CCK and GLP-1 secreted from the intestinal I-cells and L-cells stimulate each receptor and the signals are mediated through the afferent vagal nerves and NTS to reduce the expression of NPY and AgRP, and finally reduce the appetite. Stimulation of 5-HT2B receptor in the stomach by 5-HT from chromaffin cells in the intestine inhibits the release of ghrelin which stimulates the appetite through the afferent vagal nerves, and stimulation of the 5HT2C receptor in the hypothalamus stimulates POMC neurons to reduce the appetite