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]