This is a working overview of MC4R, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-06-26. Anything still debated is marked as such rather than presented as settled.
The molecular backbone consists of seven amino acid residues joined into a ring through a disulfide bridge. This cyclic conformation is critical for receptor binding. The sequence includes an acetylated N-terminus and an amidated C-terminus, modifications that improve resistance to enzymatic breakdown. One residue is in the D-configuration, a feature that further stabilizes the peptide against protease activity. Together, the ring structure and specific stereochemistry determine selectivity among melanocortin receptor subtypes.
Across literature and commercial listings, the substance appears under several names, including bremelanotide, PT-141, and various brand designations. A CAS registry number provides a unique identifier for the compound, aiding retrieval from chemical databases. Synonym lists may also contain early development codes and descriptive chemical names. When consulting sources, researchers need to confirm that the cited names refer to the same molecular structure to avoid confusion. Naming consistency matters especially when comparing analytical data across publications.
PT-141 is a synthetic cyclic heptapeptide whose development code is bremelanotide. It belongs to the class of melanocortin receptor agonists and acts by mimicking endogenous peptide hormones. The compound originated from research on melanotan II, where investigators exploring derivatives found distinct pharmacological features. Unlike the parent compound, PT-141 showed effects on pathways related to sexual desire and function in early studies, prompting its development as a separate candidate. Its molecular design aimed to separate receptor activity from pigmentary effects.
Clinical development of bremelanotide proceeded through several reformulation attempts. An early intranasal version was discontinued, and a subcutaneous auto-injector formulation later received approval for hypoactive sexual desire disorder in premenopausal women. Approval decisions have varied by country and over time, and the product has not been universally adopted. Blood pressure elevation is a documented effect, which is why some jurisdictions require monitoring after administration. The clinical evidence base continues to evolve as additional studies are published.
Bremelanotide is a cyclic heptapeptide that acts as an agonist at melanocortin receptors. It binds MC1R, MC3R, MC4R, and MC5R, with MC4R activation considered most relevant to sexual desire pathways in the central nervous system. The molecule is a synthetic analog of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation and energy regulation. Early research explored its use in tanning before attention shifted toward sexual dysfunction applications. Receptor binding affinity varies across these subtypes.
Activation of MC4R in the hypothalamus is thought to influence dopaminergic signaling, which in turn affects arousal and desire. This mechanism differs from that of phosphodiesterase type 5 inhibitors, which act primarily on vascular smooth muscle in the genital region. Because the pathway is central rather than peripheral, effects are not strictly dependent on local blood flow. The precise downstream cascade linking receptor binding to behavioral outcomes remains an area of ongoing investigation.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Cyclic peptide | Melanocortin receptor agonist family |
| Molecular weight | Approximately 1025 Da | Free base form |
| Appearance | White to off-white powder | Lyophilized product |
| Solubility | Soluble in water | Also dissolves in polar organic solvents |
| Storage temperature | -20 degrees Celsius | Dry and protected from light |
Bremelanotide acts as an agonist at several melanocortin receptors, with the strongest reported activity at MC4R and measurable activity at MC1R and MC3R. Because MC4R is expressed in hypothalamic and limbic circuits, the proposed mechanism links receptor activation to modulation of central pathways involved in desire rather than to direct effects on peripheral genital tissue. The precise downstream steps remain incompletely characterized, and evidence for the involvement of specific neurotransmitters is suggestive rather than settled. Nausea and blood pressure elevation reported during trials are consistent with melanocortin signaling outside the intended target circuit.
Compared with melanotan II, bremelanotide is a smaller cyclic peptide with a more constrained backbone, which affects receptor selectivity and metabolic stability. Published descriptions give a plasma half-life on the order of a few hours after subcutaneous administration, with elimination through hepatic and renal routes and limited plasma protein binding. Central access is inferred from effects observed in animal models, although direct measurement in humans is limited. Handling and storage requirements follow from the peptide backbone, which is susceptible to hydrolysis and oxidation.
PT-141 is the research code for bremelanotide, a cyclic heptapeptide derived from alpha-melanocyte-stimulating hormone. The molecule belongs to the melanocortin receptor agonist family and shows highest affinity for the MC4 receptor subtype, with weaker activity at MC1, MC3 and MC5. Its structure retains the core His-Phe-Arg-Trp sequence that defines melanocortin recognition, while cyclization and terminal modifications improve metabolic stability relative to the parent hormone. Early work classified the compound as a centrally acting agent rather than a peripherally acting vasodilator, which shaped subsequent development priorities.
Receptor activation in hypothalamic and limbic circuits is the mechanism most often cited for the observed effects on sexual desire. Signalling through MC4R couples to Gs proteins and raises intracellular cyclic AMP, which in turn modulates dopaminergic tone in reward-related pathways. Because the peptide reaches the central nervous system after subcutaneous administration, peripheral vascular changes are regarded as secondary rather than primary. The precise neural circuits that translate receptor occupancy into behavioural change remain incompletely mapped, and published accounts describe the pathway in general terms rather than as a fully resolved sequence.
Compared with the related compound melanotan II, PT-141 shows markedly weaker activation of receptors tied to pigmentation. This difference stems from subtle structural variations that alter affinity distribution across receptor subtypes. Investigators propose that such selectivity produces a different side effect profile in specific applications. However, downstream consequences of prolonged receptor activation remain uncertain in the literature. Published studies do not fully agree on the duration of signaling pathway activity and the mechanisms of desensitization.
From a pharmacokinetic standpoint, the peptide is usually delivered by injection because oral bioavailability is very low; proteases in the digestive tract degrade it rapidly. After subcutaneous administration, plasma concentrations reach a peak within roughly one hour. Its elimination half-life is relatively short, with most reports placing it in the range of a few hours. Nasal formulations have also been examined, though absorption varies widely between individuals. Metabolism proceeds mainly through peptidase cleavage, and the resulting products are excreted by the kidneys.
PT-141 initiates cellular signaling by binding to specific subtypes within the melanocortin receptor family. These receptors belong to the G protein-coupled receptor superfamily, and activation raises intracellular cyclic adenosine monophosphate levels. This cascade ultimately influences neuronal circuits in the central nervous system that are associated with sexual desire and arousal. Research indicates the compound's action concentrates in hypothalamic regions rather than peripheral tissues, which helps explain some observed pharmacological features. The selectivity of receptor binding underlies its functional differences.
=== Works cited === This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Alum". Encyclopædia Britannica. Vol. 1 (11th ed.). Cambridge University Press. pp. 766–767.
=== Pharmaceutical products === Several currently marketed amphetamine formulations contain both enantiomers, including those marketed under the brand names Adderall, Adderall XR, Mydayis, Adzenys ER, Adzenys XR-ODT, Dyanavel XR, Evekeo, and Evekeo ODT. Of those, Evekeo (including Evekeo ODT) is the only product containing only racemic amphetamine (as amphetamine sulfate), and is therefore the only one whose active moiety can be accurately referred to simply as "amphetamine". Dextroamphetamine, marketed under the brand names Dexedrine and Zenzedi, is the only enantiopure amphetamine product currently available. A prodrug form of dextroamphetamine, lisdexamfetamine, is also available and is marketed under the brand name Vyvanse. As it is a prodrug, lisdexamfetamine is structurally different from dextroamphetamine, and is inactive until it metabolizes into dextroamphetamine. The free base of racemic amphetamine was previously available as Benzedrine, Psychedrine, and Sympatedrine. Levoamphetamine was previously available as Cydril. Many current amphetamine pharmaceuticals are salts due to the comparatively high volatility of the free base. However, oral suspension and orally disintegrating tablet (ODT) dosage forms composed of the free base were introduced in 2015 and 2016, respectively. Some of the current brands and their generic equivalents are listed below.
=== Neutrons === After the discovery of the neutron by James Chadwick in 1932, the ultimate root cause for the existence of isotopes was clarified, that is, the nuclei of different isotopes for a given element have different numbers of neutrons, albeit having the same number of protons.
== Bibliography == Prentice, B. E., & Benell, D. (1992). "Determinants of empty returns by US refrigerated trucks: conjoint analysis approach". Canadian Journal of Agricultural Economics/Revue canadienne d'agroeconomie, 40(1), 109-127. doi:10.1111/j.1744-7976.1992.tb03680.x (abstract).
=== Antimicrobial preservatives === Antimicrobial preservatives prevent degradation by bacteria. This method is the most traditional and ancient type of preserving—ancient methods such as pickling and adding honey prevent microorganism growth by modifying the pH level. The most commonly used antimicrobial preservative is lactic acid. Common antimicrobial preservatives are presented in the table. Nitrates and nitrites are also antimicrobial. The detailed mechanism of these chemical compounds range from inhibiting growth of the bacteria to the inhibition of specific enzymes.
Sources: en.wikipedia.org
Due to the monoamine oxidase inhibitor (MAOI) activity of ayahuasca, it has a prominent risk of drug interactions with other monoaminergic agents. As an example, combination of ayahuasca with a selective serotonin reuptake inhibitor (SSRI) can result in potentially life-threatening serotonin syndrome.
== Structure == LH is a heterodimeric glycoprotein. Each monomeric unit is a glycoprotein molecule; one alpha and one beta subunit make the full, functional protein. Its structure is similar to that of the other glycoprotein hormones, follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), and human chorionic gonadotropin (hCG). The protein dimer contains 2 glycopeptidic subunits (labeled alpha- and beta- subunits) that are non-covalently associated:
However there have not been any in vivo or in vitro studies of magnetic nanoparticles being used to deliver drugs to the arteries to effectively reduce inflammation. Other potential applications of magnetic nanoparticles are brain imaging and drug delivery past the blood-brain barrier (BBB) using biodegradable magnetic iron oxide nanoparticles. The scope of this application is the treatment of central nervous system (CNS) disorders by functioning as contrast agents and drug carriers. To cross the BBB, these nanoparticles are designed by creating specificity to the BBB; this is achieved by designing the surface of the nanoparticles to be engrafted to ligands, antibodies, small molecules, cell-penetrating peptides, or conjugated RNA to target specific receptors situated along the BBB in order to facilitate entry. As opposed to methods of drug delivery that result in drugs being removed from the cerebrospinal fluid (CSF) or being degraded, magnetic nanoparticle delivery presents an opportunity to protect therapeutics as well as encourage more efficient delivery following the introduction of the nanoparticles. Magnetic nanoparticles can also be used in conjunction with imaging modalities like ultrasound to improve imaging. The use of nanoparticles in ophthalmic drug delivery is also being explored in clinical research. Magnetic nanoparticles inserted into rats' corneas or administered in an eye drop solution showed high adhesion to the target site. However, the exact mechanism by which the adhesion occurred is still being researched.
== Attenuation in eukaryotes == Although an attenuation mechanism that involves translation while transcription is ongoing, like to the mechanism for the trp operon (and some other amino acid biosynthetic operons), would not work in eukaryotes, there is evidence for attenuation in Eukaryotes. Research conducted on microRNA processing provides evidence of eukaryotic attenuation; after co-transcriptional endonucleolitical cleavage by Drosha 5'->3' exonuclease XRN2 may terminate further transcription by torpedo mechanism.
Sources: en.wikipedia.org
It belongs to the melanocortin receptor agonist family of peptides. Its cyclic structure distinguishes it from linear peptides and shapes its receptor binding profile.
It emerged from research on melanotan II. Investigators exploring derivatives observed distinct pharmacological features related to sexual function.
Common names include bremelanotide and PT-141. Chemical databases may also list early development codes and descriptive names.
PT-141 is the research code for bremelanotide, a cyclic peptide developed as a melanocortin receptor agonist. The code has appeared in literature and catalog listings since early development. Bremelanotide is the international nonproprietary name.