Melanotan II
MT-II; MT-2; melanotan-II; cyclic α-MSH analogue; non-selective melanocortin receptor agonist
Melanotan II (MT-II) is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone (α-MSH) that acts as a non-selective agonist at melanocortin receptors, with notable activity at the MC1, MC3, and MC4 subtypes. In preclinical research it has been used as a pharmacological probe to interrogate central melanocortin signaling pathways across several domains. Rodent studies have examined its effects on energy homeostasis and feeding behavior, where central administration has been associated with reduced food intake and modulation of neuropeptide Y-driven orexigenic signaling. Other animal work has investigated its influence on thermogenic capacity and brown-fat-associated gene expression, as well as on proceptive sexual behaviors in female rats. In human research, MT-II has been studied in small controlled investigations of penile erection and sexual motivation in men. Reported research domains therefore include melanocortin receptor pharmacology, ingestive behavior and metabolism, thermoregulation, and sexual physiology. Much of the literature treats MT-II as a tool compound for probing melanocortin biology rather than as an approved therapeutic, and studies frequently note dose-dependent effects and tolerability observations such as nausea and yawning.
MT-II is a cyclic α-MSH analogue that non-selectively activates melanocortin receptors (notably MC1R, MC3R, and MC4R), stimulating cyclic AMP signaling. This engagement of central and peripheral melanocortin pathways underlies the feeding, thermogenic, pigmentation-related, and sexual-behavior effects examined in research models.
Note · Single-compound peptide (not a blend). All four cited studies were verified via the NCBI E-utilities esummary API for confirmed title/author/journal/year; PubMed HTML pages returned a CAPTCHA wall, so metadata was cross-checked through the official NCBI API rather than the page itself.
In small double-blind, placebo-controlled human studies, subcutaneous Melanotan II was investigated for its effects on penile erection and self-reported sexual desire, with researchers documenting erectile responses and dose-related tolerability observations such as nausea and yawning.
In ovariectomized, hormonally primed female rats, administration of melanotan II was associated with an increase in proceptive behaviors (hops, darts, and ear-wiggling), which researchers interpreted as evidence of melanocortin involvement in female sexual motivation.
In male rats, central melanotan-II was studied for its capacity to counteract neuropeptide Y-induced increases in food intake and adiposity, with the melanocortin pathway examined as a counter-regulatory system to NPY-driven orexigenic signaling.
In a PACAP-deficient mouse model undergoing cold acclimation, daily peripheral melanotan II was examined for its effect on noradrenaline-induced metabolic rate, where it was associated with partial restoration of impaired thermogenic capacity.
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