Melanocortin receptors are members of the rhodopsin family of 7-transmembrane G protein-coupled receptors.
There are five known members of the melanocortin receptor system[1] each with differing specificities for melanocortins:[2][3][4] These receptors are inhibited by endogenous inverse agonists agouti signalling peptide and agouti-related peptide,[7] and activated by synthetic (i.e. afamelanotide) and endogenous agonist melanocyte-stimulating hormones.
[8] Several selective ligands for the melanocortin receptors are known,[9][10][11][12] and some synthetic compounds have been investigated as potential tanning, anti-obesity and aphrodisiac drugs, with tanning effects mainly from stimulation of MC1,[13] while anorectic and aphrodisiac effects appear to involve both MC3 and MC4.
[14] MC1, MC3 and MC4 are widely expressed in the brain, and are also thought to be responsible for effects on mood and cognition.
[15][16][17][18]