Melanocortin Receptor

Melanocortin receptors (MC1R through MC5R) are a family of G protein-coupled receptors activated by melanocortin peptides — alpha-MSH, ACTH, and related molecules. They're distributed throughout the body and the brain, with different subtypes doing different things. MC1R: skin pigmentation and anti-inflammation. MC3R: energy balance and inflammation. MC4R: appetite suppression, sexual function, and autonomic regulation of metabolism. MC2R: ACTH receptor on the adrenal cortex — drives cortisol production. Three peptides on this site work through the melanocortin system: PT-141 (bremelanotide) acts on MC3R and MC4R — the sexual arousal mechanism is MC4R-mediated in the hypothalamus, which is why it works differently from sildenafil (which is a vascular drug). This is why PT-141 is the only FDA-approved treatment for HSDD that works centrally rather than peripherally. Semax acts partly through MC4R and MC5R — the neurotrophic and cognitive effects may be melanocortin-mediated alongside its BDNF activity. KPV (Lys-Pro-Val), the C-terminal fragment of alpha-MSH, retains alpha-MSH's anti-inflammatory activity via MC1R.