Melanocortin peptides interact with the melanocortin receptor family (MC1R through MC5R), a group of G protein-coupled receptors with diverse physiological roles. PT-141 (Bremelanotide), the primary compound in this category, is a cyclic heptapeptide derived from Melanotan II that acts as an agonist at MC3R and MC4R. Unlike direct vascular-acting compounds, PT-141 operates through central nervous system melanocortin receptor pathways, making it a subject of ongoing research interest in neuroendocrine signaling models. Supplied as lyophilized powder with purity >99% verified by independent third-party HPLC analysis. For in vitro laboratory research use only.