G protein-coupled receptors in gastrointestinal physiology II. Regulation of neuropeptide receptors in enteric neurons

Neuropeptides exert their diverse biological effects by interacting with G protein-coupled receptors (GPCRs). In this review we address the question. What regulates the ability of a target cell, in particular a neuron, to respond to a neuropeptide? Available evidence from studies of many GPCRs in reconstituted systems and transfected cell lines indicates that much of this regulation occurs at the level of the receptor and serves to alter the capacity of the receptor to bind ligands with high affinity and to couple to heterotrimeric G proteins. Although some of the knowledge gained from these studies is applicable to the regulation of neuropeptide receptors on neurons, at present there are far more questions than answers.