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Research guide

PT-141

Cyclic heptapeptide derived from Melanotan II with reduced MC1R activity and preserved MC3R/MC4R agonism. Used to study hypothalamic MC4R signalling, MC4R-oxytocin axis, and central melanocortin-mediated autonomic and reward circuits.

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Short answer

PT-141 is supplied by HALO as a research-use-only lyophilized compound for qualified laboratory research. Cyclic heptapeptide derived from Melanotan II with reduced MC1R activity and preserved MC3R/MC4R agonism. Used to study hypothalamic MC4R signalling, MC4R-oxytocin axis, and central melanocortin-mediated autonomic and reward circuits.

  • Molecular weight: 1,025.2 g/mol
  • CAS: 189691-06-3
  • Available sizes: 10 mg
  • Documentation: 98%+ HPLC purity, independent COA, lot-indexed records
  • Use limitation: Research use only; not for human or veterinary use

Diagrams

BDNFGABAHPAReceptorResearch pathway (RUO model)
Research pathway context (schematic)
HALO · IDENTITYPT-141CAS: 189691-06-3MW: 1,025.2 g/molPurity ≥98% HPLC · Lyophilized · RUO only
Identity card
VialLot matchHPLCLC-MSBatch-specific COA chain
COA verification flow
Lyophilized handling (lab)−20 °CDry/sealed→Reconst.Diluent→2–8 °CShort holdResearch stock prep only · not dosing guidance
Lyophilized handling workflow

Mechanism of action in research models

MC4R agonism in hypothalamic research: high-affinity MC4R agonism in the paraventricular nucleus (PVN), medial preoptic area (MPOA), and ventromedial hypothalamus — regions involved in autonomic control, reproductive behaviour, and energy homeostasis. PT-141’s MC4R agonism activates Gs-cAMP signalling in these neurones, modulating oxytocin release from the PVN, dopamine release in the mesolimbic pathway, and autonomic outflow to peripheral targets.

MC3R agonism: MC3R is expressed in the hypothalamic arcuate nucleus and brainstem (autoreceptor on POMC neurones) and in peripheral immune cells. PT-141’s MC3R agonism enables research into MC3R’s role in energy balance, immune modulation, and negative-feedback control of the melanocortin system. Differential MC3R vs MC4R contributions are dissected using selective antagonists (SHU9119 at low concentrations for MC3R; HS024 for MC4R).

Dopaminergic interactions: PT-141 and other MC4R agonists increase dopamine release in the nucleus accumbens in rodent models, suggesting interactions between melanocortin signalling and the mesolimbic reward pathway.

Oxytocin signalling: MC4R agonism in the PVN stimulates oxytocin release into both the hypothalamic portal circulation and the general circulation — providing a research tool for studying the melanocortin-oxytocin axis in reproductive and social-behaviour neuroscience models.

Research background and peer-reviewed literature

PT-141 evolved from the Melanotan programme initiated by Victor Hruby’s group at the University of Arizona, which systematically explored α-MSH analogues to create potent, metabolically stable melanocortin-receptor agonists. The PT-141/Bremelanotide modifications (deacetyl N-terminus; C-terminal hydroxyl instead of amide) reduce MC1R affinity while preserving MC3R/MC4R affinity, optimising CNS selectivity. Wessells et al. published pivotal research characterising PT-141 in male rat models, documenting MC4R-dependent responses at dose ranges that avoided the blood-pressure effects observed with MT-II. The melanocortin system has been studied in the broader context of energy-homeostasis research, particularly POMC/CART vs NPY/AgRP neurone interactions in the arcuate nucleus.

Reconstitution and storage protocol

  1. Allow vial to equilibrate to room temperature before opening.
  2. Reconstitute in bacteriostatic water or sterile PBS. PT-141 is water-soluble; 1–2 mg/mL is practical for research stocks.
  3. Add diluent slowly along the vial wall; swirl gently to dissolve.
  4. Filter through 0.22 μm for sterile cell-culture or in-vivo applications.

Storage: lyophilized at −20 °C, sealed, desiccated, light-protected (stable 24+ months). Reconstituted at 4 °C for up to 28 days; aliquot at −80 °C for extended storage.

Frequently asked research questions

What receptors does PT-141 target, and why does this matter for research?
High-affinity MC3R and MC4R agonism with substantially reduced MC1R activity compared to Melanotan II. MC1R activation causes pigmentation and facial flushing in animal models — complicating CNS research. MC3R is relevant to energy balance and immunomodulation. MC4R is the key CNS receptor in the PVN and limbic system — the primary target for studies of central arousal, reward signalling, and autonomic output. PT-141’s reduced MC1R activity allows CNS MC3R/MC4R research without confounding peripheral melanocyte effects.
How is PT-141 different from Melanotan II?
Two structural differences: (1) PT-141 removes MT-II’s N-terminal acetyl group; (2) replaces MT-II’s C-terminal amide with a hydroxyl group. These reduce MC1R affinity while preserving MC3R/MC4R affinity — producing CNS-mediated MC4R responses without the transient blood-pressure increases and nausea observed with MT-II in rodent models.
What CNS circuits are studied using PT-141 as a research tool?
(1) MC4R–oxytocin axis in the PVN; (2) MC4R–dopamine interactions in the mesolimbic pathway; (3) hypothalamic energy-balance circuits — MC3R/MC4R’s role in POMC/NPY neurone crosstalk in the arcuate nucleus; (4) autonomic-output pathways from the PVN and spinal cord. All applications are for qualified laboratory research use only.
What concentrations are used in in-vitro melanocortin-receptor assays?
In cell-based assays using recombinant MC3R- or MC4R-expressing lines (HEK293, CHO), PT-141 shows high-affinity receptor binding in the sub-nanomolar to nanomolar range (EC50 ~1–10 nM for MC4R). For cAMP-accumulation assays measuring Gs-coupled activation, the functional EC50 in MC4R-expressing cell lines is typically 1–50 nM. In-vivo rodent experiments have used 0.1–10 mg/kg ranges depending on the endpoint.

Selected references

  1. Cai M, Hruby VJ. “The Melanocortin Receptor System: A Target for Multiple Degenerative Diseases.” Curr Protein Pept Sci. 2016;17(5):488-496. PMID: 26916163
  2. Wikberg JE. “Melanocortin receptors: perspectives for novel drugs.” Eur J Pharmacol. 1999;375(1-3):295-310. PMID: 10443584
  3. Rosen RC, et al. “Evaluation of the safety, pharmacokinetics and pharmacodynamic effects of subcutaneously administered PT-141, a melanocortin receptor agonist, in healthy male subjects and in patients with an erectile dysfunction.” Int J Impot Res. 2004;16(2):135-142. PMID: 14999221
  4. Vrinten DH, et al. “Antagonism of the melanocortin system reduces cold and mechanical allodynia in mononeuropathic rats.” J Neurosci. 2000;20(21):8131-8137. PMID: 11050135

Research use only. Materials are sold strictly for in vitro and qualified laboratory research. Not for human or veterinary use, diagnosis, or treatment. Full text: Research Use Statement.