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PT-141 (Bremelanotide)

PT-141 (bremelanotide, CAS 189691-06-3) is a synthetic cyclic heptapeptide lactam and a structural analog of Melanotan-2 with selective activity at MC3R and MC4R, having a molecular weight of approximately 1,025.2 Da and formula C₅₀H₆₈N₁₄O₁₀. The key structural difference from MT-2 — replacement of the C-terminal amide with a free carboxylic acid — reduces MC1R-mediated pigmentation effects while preserving central MC3R/MC4R activity. PT-141 is a premier research tool for studying melanocortin-mediated sexual function, CNS melanocortin signaling, and MC4R pharmacology independent of melanogenic effects.

Technical Specifications

Property Value
CAS Number 189691-06-3
Molecular Formula C₅₀H₆₈N₁₄O₁₀
Molecular Weight ~1,025.2 Da
Purity ≥99% (HPLC-verified)
Appearance Lyophilized white powder
Solubility Soluble in sterile water and aqueous buffers
Storage -20°C (lyophilized), 2–8°C (reconstituted)

Mechanism of Action

PT-141 functions as a centrally acting melanocortin receptor agonist, with primary activity at MC3R and MC4R. MC4R activation in the hypothalamic paraventricular nucleus (PVN) stimulates oxytocinergic neurons that project to the lumbosacral spinal cord, where they enhance parasympathetic (pelvic nerve) outflow to genital tissues. This MC4R-oxytocin-parasympathetic pathway increases blood flow and smooth muscle relaxation in erectile tissue through nitric oxide (NO)/cGMP signaling independently of the dopaminergic pathways targeted by PDE5 inhibitors. MC3R activation, primarily in the arcuate nucleus and limbic system, modulates dopaminergic and serotonergic neurotransmission, contributing to the motivational and arousal components of sexual behavior. Unlike Melanotan-2, PT-141's reduced affinity for MC1R substantially diminishes the melanogenesis side effects (skin darkening), making it a cleaner pharmacological probe for central MC3R/MC4R function. The peptide is active when administered to CNS-accessible compartments, as its effects require central receptor engagement at hypothalamic and brainstem sites.

Research Applications

  • Primary: Central MC4R pharmacology — melanocortin-mediated sexual function, autonomic nervous system regulation
  • Secondary: MC3R signaling in motivation/reward pathways, oxytocin neuron modulation, sexual arousal neurobiology
  • Model Systems: In vitro (MC3R/MC4R-transfected cell lines, cAMP accumulation assays), in vivo (sexual behavior paradigms in rodent models, CNS melanocortin microinjection studies)

Quality Control & Analytical Methods

  • HPLC: ≥99% purity verification at 214/220 nm (C18 reversed-phase column)
  • Mass Spectrometry: ESI-MS for molecular weight confirmation (~1,025.2 ±1.0 Da)
  • Peptide Content: Amino acid analysis (AAA) for net peptide content determination
  • Endotoxin: <1 EU/mg (LAL assay)
  • TFA Content: <1% (ion chromatography)

Stability & Storage

Condition Stability
-20°C (lyophilized) 24 months
4°C (lyophilized) 6 months
25°C (lyophilized) 1 month
Reconstituted (4°C) 7 days
Reconstituted (-20°C) 30 days

Key Research References

  • Molinoff et al. (2003) — PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. PMID: 12851337
  • Wessells et al. (2000) — Effect of an α-MSH analog (PT-141) on penile erection and sexual behavior. Peptides. PMID: 11228115
  • Pfaus et al. (2007) — Melanocortins, sexual behavior, and the brain. Horm Behav. PMID: 17555716

Source & Purchase

For researchers requiring research-grade PT 141 with full analytical documentation including HPLC, LC-MS, and Certificate of Analysis, visit the HK Peptides product page for specifications, bulk pricing, and ordering.

View PT 141 Product →

FAQ

Q: What purity level is standard for PT-141? A: HK Peptides supplies PT-141 at ≥99% purity by HPLC with full COA documentation.

Q: How should PT-141 be stored for research use? A: Lyophilized PT-141 should be stored at -20°C. Reconstituted solutions at 4°C for short-term use (up to 7 days).