α-MSH free acid (α-Melanocyte-Stimulating Hormone free acid) is an MC3R and MC4R agonist with EC50s of 0.16 nM and 5.6 nM, respectively. α-MSH free acid activates cAMP generation at MC3R and MC4R[1].
MC3R: 0.16 nM (EC50); MC4R: 5.6 nM (EC50)
[1] Miwa H, et al. Structural determinants of the melanocortin peptides required for activation of melanocortin-3 and melanocortin-4 receptors. J Pharmacol Exp Ther. 1995;273(1):367-372. PMID:7714790
