Source comparison
Melanotan-2 Mechanism: MC1R vs MC4R Receptor Activation
Melanotan-2 binds to at least four melanocortin receptor subtypes (MC1R, MC3R, MC4R, MC5R), but the effects men care about come primarily from MC1R and MC4R activation. MC1R receptors are concentrated in epidermal melanocytes. When MT-2 binds, it activates ade
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- Melanotan-2 binds to at least four melanocortin receptor subtypes (MC1R, MC3R, MC4R, MC5R), but the effects men care about come primarily from MC1R and MC4R activation. MC1R receptors are concentrated in epidermal melanocytes. When MT-2 binds, it activates adenylyl cyclase, increasing cyclic AMP (cAMP) levels, which upregulates tyrosinase, the rate-limiting enzyme in melanin synthesis. This triggers eumelanin production within hours, but visible tanning requires cumulative dosing over 7–14 days because melanin must migrate from melanocytes to keratinocytes in the outer skin layers.
- MC4R receptors are concentrated in the central nervous system, particularly the paraventricular nucleus (PVN) of the hypothalamus and the spinal ejaculatory centers. When MT-2 binds MC4R, it increases pro-opiomelanocortin (POMC) signaling, which elevates dopamine and triggers nitric oxide synthase (NOS) activity in the corpus cavernosum. The erectile tissue mechanism. This is why spontaneous erections occur 4–6 hours post-injection even without sexual stimulation. A 2000 study in the International Journal of Impotence Research demonstrated that MT-2 at 0.025mg/kg produced erections in men with psychogenic erectile dysfunction who had failed sildenafil trials, suggesting the mechanism bypasses typical vascular pathways.
- The dual-receptor activity creates a dosing problem: the threshold for tanning (MC1R-driven) is lower than the threshold for sexual effects (MC4R-driven). Men using MT-2 strictly for tanning at 0.01mg/kg often report mild facial flushing and nausea but minimal erectile effects, while those using 0.025–0.03mg/kg for sexual function experience pronounced tanning as a secondary effect. You can't selectively activate one receptor without the other. The peptide is nonselective.