Melanocyte stimulating hormone release inhibiting factor,(C₁₃H₂₄N₄O₃), a tri-peptide with the sequence H2N-Pro-Leu-Gly-amide, MW= 284.35. Melanocyte-inhibiting factor (also known as Pro-Leu-Gly-NH₂, Melanostatin, MSH release-inhibiting hormone or MIF-1) is an endogenous peptide fragment derived from cleavage of the hormone oxytocin, but having generally different actions in the body⁽¹⁾. MIF-1 produces multiple effects, both blocking the effects of opioid receptor activation⁽²⁾, while at the same time acting as a positive allosteric modulator of the D₂and D₄dopamine receptor subtypes, as well as inhibiting release of other neuropeptides such as alpha-MSH, and potentiating melatonin activity⁽³⁾. MIF-1 is unusually resistant to metabolism in the bloodstream, and crosses the blood–brain barrier easily, though it is poorly active orally and is usually injected.

Figure1 Formula of Melanocyte stimulating hormone release inhibiting factor

Ref:

1. Celis ME, Taleisnik S, Walter R (July 1971). "Regulation of formation and proposed structure of the factor inhibiting the release of melanocyte-stimulating hormone".Proceedings of the National Academy of Sciences of the United States of America68 (7): 1428–33.

2. Contreras PC, Takemori AE (June 1984). "Effect of prolyl-leucyl-glycinamide and alpha-melanocyte-stimulating hormone on levorphanol-induced analgesia, tolerance and dependence".Life Sciences34 (26): 2559–66.

3. Sandyk R (May 1990). "MIF-induced augmentation of melatonin functions: possible relevance to mechanisms of action of MIF-1 inmovement disorders".The International Journal of Neuroscience52 (1-2): 59–65.