If you have been reading about alpha-MSH and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-10-26. Numbers and descriptions here follow the published literature rather than marketing material.
The melanocortin system comprises five G protein-coupled receptors, designated MC1 through MC5, that signal mainly through cyclic AMP accumulation. MC1R and MC2R are associated with pigmentation and adrenal steroid production, while MC3R and MC4R are expressed in the central nervous system and influence energy balance and behavior. MC5R appears in exocrine tissues. Natural agonists include alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone, and endogenous antagonists such as agouti-related protein modulate the same sites. This receptor family provides the framework within which bremelanotide activity is described.
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.
Identity and purity are usually established with reversed-phase high-performance liquid chromatography combined with mass spectrometry. A gradient of water and acetonitrile containing trifluoroacetic acid is a common mobile phase, and ultraviolet detection near 214 nanometres responds to the peptide backbone. Mass spectrometry confirms the expected molecular mass and helps reveal truncation or oxidation products. Purity is reported as a peak-area percentage, a figure that depends on the wavelength and gradient used, so values from different laboratories are not always directly comparable. Peptide mapping and amino acid analysis provide additional confirmation when required.
Regulatory status varies by jurisdiction, where approved prescription products, compounded preparations and research-grade material are treated as distinct categories with different documentation requirements. Suppliers of research material commonly issue a certificate of analysis listing purity, identity and sometimes endotoxin content. Independent verification by a third-party laboratory is often recommended because self-reported figures are difficult to check. Literature discussions usually state the source, purity and storage conditions of the material used, since these details affect reproducibility. Analysts note that a reported purity figure does not by itself describe biological activity.
Lyophilised peptide is generally held below minus twenty degrees Celsius, protected from light and moisture, because hydrolysis and oxidation accumulate faster at ambient temperature. Once reconstituted, solutions are typically kept between two and eight degrees Celsius and used within a short window defined by the supplier. Repeated freeze-thaw cycles are avoided since they promote aggregation and loss of soluble material. Container material matters as well, because peptides adsorb to certain plastics and glass surfaces at low concentration. Stability figures supplied by a vendor apply only to the specific lot and buffer that were tested.
| Property | Value | Notes |
|---|---|---|
| Primary receptor target | MC4R | Highest reported agonist potency within the family |
| Secondary receptor activity | MC1R and MC3R | Lower potency than at MC4R |
| Elimination half-life | About 2 to 3 hours | Measured after subcutaneous administration |
| Plasma protein binding | Approximately 44 percent | Species- and assay-dependent |
| Route of administration | Subcutaneous injection | Reviewed product uses a single-use device |
Handling procedures emphasize minimizing moisture uptake, since the dried solid is hygroscopic and can draw water when warmed to room temperature before a vial is opened. Laboratories record lot number, purity, counter-ion content, and residual solvent data supplied by the producer. Impurity profiles are compared run to run, and any shift in retention time or peak shape prompts re-verification against a reference standard. Certificates of analysis are treated as claims to be checked rather than accepted at face value.
Identity and purity testing for this peptide typically relies on reversed-phase high-performance liquid chromatography with ultraviolet detection, reported as area-percent purity. Mass spectrometry, usually in tandem mode, confirms molecular mass and supports quantification in biological matrices. Sequence confirmation may use peptide mapping after enzymatic digestion, while nuclear magnetic resonance and circular dichroism supply supplementary structural detail. No single technique establishes identity alone, so laboratories compare retention time, mass, and fragment pattern against a verified reference standard.
The lactam ring that closes the peptide backbone improves resistance to exopeptidase attack, but the molecule stays susceptible to hydrolysis and oxidation once dissolved. Degradation accelerates with temperature, extreme pH, and light exposure, and repeated freeze-thaw cycles promote aggregation and material loss. Lyophilized powder held desiccated at or below minus twenty degrees Celsius is the common way to keep reference material. Reconstituted solutions are generally kept cold and used within a short window because their stability is far lower than that of the dry solid.
Whether the behavioral effect originates centrally, peripherally, or through both remains an active question. Animal experiments using receptor antagonists and site-specific injections point toward hypothalamic melanocortin circuits as a key locus, but translating those findings to humans is not straightforward. Blood pressure changes observed in trials suggest a vascular component that may be peripherally mediated. The relationship between receptor occupancy and reported effect has not been mapped in humans, and no validated biomarker predicts response. This gap makes it difficult to explain individual variability on pharmacological grounds alone.
Bremelanotide acts as an agonist at melanocortin receptors, a family of five G-protein-coupled receptors labeled MC1 through MC5. Binding studies indicate activity at several of these subtypes rather than strict selectivity for one. Signalling proceeds mainly through Gs-mediated activation of adenylyl cyclase, raising intracellular cyclic AMP. The MC4 receptor, expressed in hypothalamic and limbic circuits, is widely regarded as the subtype most relevant to sexual response. Because the molecule is not subtype-selective, effects at other melanocortin receptors are expected and are used to explain some observed side effects.
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.
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.
PT-141 is the research designation for bremelanotide, a synthetic cyclic heptapeptide developed as a melanocortin receptor agonist. The peptide contains seven amino acids with an internal lactam bridge that constrains the backbone into a stable ring. Cyclisation of this kind improves resistance to enzymatic degradation relative to linear analogues. The compound was first explored for effects on melanin production, because several melanocortin receptors influence pigmentation. Its later association with sexual desire emerged from observations made during that early work, and the molecule became the subject of a separate development programme.
Bremelanotide is a moderately large peptide with a molecular mass near 1025 daltons. In lyophilised form it appears as a white to off-white powder and is freely soluble in water and other polar solvents. The intact lactam ring is essential for receptor affinity, while linearised fragments bind far more weakly. Solutions are sensitive to extremes of pH and to prolonged exposure to light and heat, so handling typically involves buffered conditions and cold storage. Its short plasma half-life reflects rapid distribution and clearance rather than chemical breakdown inside the vial.
==== Low sex hormone levels ==== Clinical studies have consistently associated medical and recreational opioid use with hypogonadism (low sex hormone levels) in different sexes. The effect is dose-dependent. Most studies suggest that the majority (perhaps as much as 90%) of chronic opioid users develop hypogonadism. A 2015 systematic review and meta-analysis found that opioid therapy suppressed testosterone levels in men by about 165 ng/dL (5.7 nmol/L) on average, which was a reduction in testosterone level of almost 50%. Conversely, opioid therapy did not significantly affect testosterone levels in women. However, opioids can also interfere with menstruation in women by limiting the production of luteinizing hormone (LH). Opioid-induced hypogonadism likely causes the strong association of opioid use with osteoporosis and bone fracture, due to deficiency in estradiol. It also may increase pain and thereby interfere with the intended clinical effect of opioid treatment. Opioid-induced hypogonadism is likely caused by their agonism of opioid receptors in the hypothalamus and the pituitary gland. One study found that the depressed testosterone levels of heroin addicts returned to normal within one month of abstinence, suggesting that the effect is readily reversible and is not permanent. As of 2013, the effect of low-dose or acute opioid use on the endocrine system is unclear. Long-term use of opioids can affect the other hormonal systems as well.
For example, enteric coatings only dissolve in the basic environment of the intestines. Drugs held in solution do not need to be dissolved before being absorbed. Lipid-soluble drugs are absorbed more rapidly than water-soluble drugs.
Chemical information, Clinical information and Biochemical information. The chemical data includes >40,000 metabolite structures with detailed descriptions, extensive chemical classifications, synthesis information and observed/calculated chemical properties. It also contains nearly 10,000 experimentally measured NMR, GC-MS and LC/MS spectra from more than 1,100 different metabolites. The clinical information includes data on >10,000 metabolite-biofluid concentrations, metabolite concentration information on more than 600 different human diseases and pathway data for more than 200 different inborn errors of metabolism. The biochemical information includes nearly 6,000 protein (and DNA) sequences and more than 5,000 biochemical reactions that are linked to these metabolite entries. The HMDB supports a wide variety of online queries including text searches, chemical structure searches, sequence similarity searches and spectral similarity searches. This makes it particularly useful for metabolomic researchers who are attempting to identify or understand metabolites in clinical metabolomic studies. The first version of the HMDB was released in Jan. 1 2007 and was compiled by scientists at the University of Alberta and the University of Calgary. At that time, they reported data on 2,500 metabolites, 1,200 drugs and 3,500 food components. Since then these scientists have greatly expanded the collection. The version 3.5 of the HMDB contains >16,000 endogenous metabolites, >1,500 drugs and >22,000 food constituents or food metabolites.
== Chromosome and gene abnormalities == Most cases of MFS have tumor cells that contain complex chromosome and/or gene abnormalities including ring chromosomes (i.e. chromosome whose ends are fused together to form a ring), double minutes (i.e. small fragments of extrachromosomal DNA), chromosomes with deletions of part of their genetic material, and chromosome translocations (i.e. abnormal switches in genetic material between different chromosomes). There were no apparent differences in these abnormalities between lower grade and higher grade tumors but their numbers were higher and more prevalent in recurrent tumors. These forms of chromosome/gene cytogenetic alterations are commonly found in various tumor types regardless of their grade or severity. Tumor cell mutations or deletions in the NF1 gene occur ~10% of MFS cases while mutations in the CDKN2A/CDKN2B and amplifications in the CDK6, CCND1, and MDM2 genes occur in rare MFS cases. While the cells in many tumor types express specific chromosome/gene abnormalities that help in determining their diagnoses, the cited chromosome and gene abnormalities discovered in TBS tumor cells have not yet been found specific enough to be of help in diagnosing MFS. The chromosome/gene abnormalities have not yet been defined in the epithelioid variant of MFS.
Sources: en.wikipedia.org
=== Supreme Council of Colon === Cassard departed from New York City and arrived in the port of Santiago de Cuba in December 1859, personally despatched by Albert Pike. When he arrived in the city, he never left the ship. Since there was an active warrant for his arrest in Cuba, he was afraid that if he did disembark, he might have been taken into custody and executed. On December 27, 1859, in the cabin of his ship, Andrés Cassard established a Supreme Council of the Ancient and Accepted Scottish Rite, 33°, at the direction of the Supreme Council, 33°, Southern Jurisdiction. The first Grand Commander of the Supreme Council was Antonio Vinent y de Gola, V Marqués de Palomares del Duero, one of the wealthiest property owners in Oriente Province. He had earned the title of Marquis in the service of the government against the independence movement. In 1860, a rift started to form between the Grand Lodge of Colon and the Supreme Council of Colon. This rift between the Supreme Council and the Grand Lodge was about more than the ability to charter Lodges, it was deeply rooted in the different political ideologies between Protestants and Catholics. While Freemasons in the capitol in Havana maintained closer links to the United States, the Eastern city of Santiago de Cuba was much closer culturally to the Catholicism in the rest of Latin America. Being predominately Catholic landowners, the Supreme Council viewed the Grand Lodge as one filled with Protestantism and Anglo-Saxon ideas.
== Epidemiology == Chronic wounds mostly affect people over the age of 60. The incidence is 0.78% of the population and the prevalence ranges from 0.18 to 0.32%. As the population ages, the number of chronic wounds is expected to rise. Ulcers that heal within 12 weeks are usually classified as acute, and longer-lasting ones as chronic.
==== Adverse effects ==== Cannabidiol use is associated with a reduction in appetite, diarrhoea, dry mouth, sedation and dizziness. These adverse events are mild and generally diminish with continued use. Additionally, an increased risk of blurred vision and interference with liver function with elevated levels of liver enzymes are reported. Due to potential liver injury, dose adjustment may be required in patients with liver diseases or taking other medications that interfere with the metabolism of cannabidiol.
== References == This article was adapted from the following source under a CC BY 4.0 license (2020) (reviewer reports): Tyler Rushton; Dworkin, Sebastian (2020). "Grainyhead-like Genes in Regulating Development and Genetic Defects" (PDF). WikiJournal of Science. 3 (1): 2. doi:10.15347/wjs/2020.002. Wikidata Q86158992.
power reactors are intended to produce heat for nuclear power, either as part of a generating station or a local power system such as a nuclear submarine. research reactors are intended to produce neutrons and/or activate radioactive sources for scientific, medical, engineering, or other research purposes. breeder reactors are intended to produce nuclear fuels in bulk from more abundant isotopes. The better known fast breeder reactor makes 239Pu (a nuclear fuel) from the naturally very abundant 238U (not a nuclear fuel). Thermal breeder reactors previously tested using 232Th to breed the fissile isotope 233U (thorium fuel cycle) continue to be studied and developed. While, in principle, all fission reactors can act in all three capacities, in practice the tasks lead to conflicting engineering goals and most reactors have been built with only one of the above tasks in mind. (There are several early counter-examples, such as the Hanford N reactor, now decommissioned). As of 2019, the 448 nuclear power plants worldwide provided a capacity of 398 GWE, with about 85% being light-water cooled reactors such as pressurized water reactors or boiling water reactors. Energy from fission is transmitted through conduction or convection to the nuclear reactor coolant, then to a heat exchanger, and the resultant generated steam is used to drive a turbine or generator.
Sources: en.wikipedia.org
=== Preclinical === AB-300 (AB300) – non-hallucinogenic serotonin 5-HT2A and 5-HT2C receptor agonist AB-5006 (AX-5006) – Escherichia coli csgA protein aggregation inhibitor and gastrointestinal microbiome modulator [96] AEX-23 – orexin OX1 receptor agonist and α-synuclein aggregate/modulator [97] Afamelanotide ([Nle4,DPhe7]-α-MSH; CUV-1647; EPT-1647; Melanotan I; Melanotan; MT-I; Prenumbra; Scenesse) – melanocortin receptor agonist [98] Alpha-synuclein aggregation inhibitor (ACI-5755; morphomer α-synuclein) – α-synuclein inhibitor [99] BEBT-758 – RNA interference and α-synuclein expression inhibitor [100] Bevemipretide (SBT-272) – cardiolipin ligand and stabilizer [101] BSC-3301 – receptor-interacting serine/threonine-protein kinase 1 (RIPK1) inhibitor [102] BXQ-350 (SapC; SapC-DOPS; sphingolipid activator protein C) – sphingomyelin phosphodiesterase stimulant and sphingosine 1-phosphate stimulant [103] Cannabidiol (CBD) – cannabinoid receptor modulator and other actions [104] Carbon monoxide (CO; HBI-002) – heme oxygenase 1 modulator [105] CB-401 – amyloid β-protein modulator [106] CBT-102 – undefined mechanism of action [107] CJRB-301 (MRx-0005) – bacteria replacement and microbiome modulator [108] CJRB-302 (MRx-0029) – bacteria replacement and microbiome modulator [109] CK-0803 – regulatory T-lymphocyte replacement [110] CU-13001 – 15-lipoxygenase (15-LOX/ALOX15) inhibitor [111] EHP-102 (VCE-003.2) – cannabinoid CB2 receptor agonist and peroxisome proliferator-activated receptor alpha (PPARα) modulator (cannabigerol (CBG) derivative) [112] Estianeptine ((S)-tianeptine; TNX-4300) – peroxisome proliferator-activated receptor PPARβ/δ and PPARγ agonist [113] FHL-401 – toll-like receptor 2 antagonist [114] FHL-701 – interleukin-12 (IL-12) subunit p40 inhibitor [115] FKK-01PD (FKK-01PD; TGHW-01AP; apomorphine prodrug) – non-selective dopamine receptor agonist and other actions [116] HT-4403 – leucine-rich repeat kinase 2 (LRRK2) inhibitor [117] IC-100 (ICCN-100) – various actions [118] KFRX-05 (BK-40195) – leucine-rich repeat kinase 2 (LRRK2) inhibitor and protein tyrosine kinase inhibitor [119] KP-405 – undefined mechanism of action [120] LB-P4 – bacteria replacement and microbiome modulator [121] Mbiotix – bacteria replacement and microbiome modulator [122] ML-021 – muscarinic acetylcholine M4 receptor antagonist [123] MP-201 – 2,4-dinitrophenol (DNP) prodrug and various actions [124] NB-003 – gene transference and parkin protein replacement [125] NB-129 – undefined mechanism of action [126] NLY-02 – glial cell inhibitor [127] NLY-03 – undefined mechanism of action [128] NNI-362 – 70 kDa ribosomal protein S6 kinase modulator [129] NRG-5051 – mitochondrial permeability transition pore inhibitor [130] PMN-442 – monoclonal antibody against α-synuclein [131] PP-003 – α-synuclein degrader [132] Research programme: 3100 programme - DigmBio/Daegu Catholic University – G protein-coupled receptor (GPCR) modulators [133] Research programme: enzyme targeted therapeutics - Nitrase Therapeutics – enzyme modulators and α-synuclein inhibitors [134] Research programme: neurodegenerative disease therapeutics - Caraway Therapeutics – autophagy stimulants and MCOLN1 stimulants [135] RGL-193 – undefined mechanism of action [136] ST-502 – gene therapy and α-synuclein genetic transcription inhibitor [137] Tomaralimab (NM-101; NM-102; NM-103; OPN-305) – monoclonal antibody against toll-like receptor 2 [138] Zervimesine (CT-1812; Elayta) – sigma σ2 receptor antagonist [139]
By the mid-1990s, several GH companies had sponsored or publicized research into the quality of life of adults with severe GH deficiency. Most were people having been treated with GH in childhood for severe deficiency. Many of them stopped injections as they reached their final heights in the low-normal range. However, as adults in their 30s and 40s, these people, who had been children with growth hormone deficiency, were now adults with growth hormone deficiency and had more than their share of common adult problems: reduced physical, mental, and social energy, excess adipose and diminished muscle, diminished libido, poor bone density, higher cholesterol levels, and higher rates of cardiovascular disease. Research trials soon confirmed that a few months of GH could improve nearly all of these parameters. However, despite marketing efforts, most GH-deficient adults remain untreated. Though GH use was slow to be accepted among adults with GH deficiency, similar research to see if GH treatment could slow or reverse some of the similar effects of aging attracted much public interest. The most publicized trial was reported by Daniel Rudman in 1990. As with other types of hormone supplementation for aging (testosterone, estrogen, DHEA), confirmation of benefit and accurate understanding of risks has been only slowly evolving. In 1997, Ronald Klatz of the American Academy of Anti-Aging Medicine published Grow Young With HGH: The Amazing Medically Proven Plan To Reverse the Effects Of Aging, an uncritical touting of GH as the answer to aging.
=== Meteoritic quinones === A proposed alternative source to chemiosmotic energy developing across membranous structures is if an electron acceptor, ferricyanide, is within a vesicle and the electron donor is outside, quinones transported by carbonaceous meteorites pick up electrons and protons from the donor. They would release electrons across the lipid membrane by diffusion to ferricyanide within the vesicles and release protons which produces gradients above pH 2, the process is conducive to the development of proton gradients.
==== Systemic sickness ==== Since the 1990s, reviews of studies for causal relations between silicone-gel prosthetic breasts and systemic disease reported no causal relation to the occurrences of either systemic or autoimmune diseases; nonetheless, many women reported suffering neurological and rheumatological illnesses caused by failures of their prosthetic breasts. The study Long-term Health Status of Danish Women with Silicone Breast Implants (2004), reported that in relation to women of the general population, women with prosthetic breasts did not have a greater rate of incidence and diagnosis of autoimmune disease; that their rate of incidence for musculoskeletal disease was lower than the rate of incidence among women who had undergone other types of cosmetic surgery.
On February 2, 2017, GNC threatened to sue the Fox Broadcasting Company for "significant economic and reputational damages, lost opportunities, and consequential damages", after an advertisement for the chain was blocked from airing during Super Bowl LI. Despite repeated approvals by Fox, the network stated that the ad had been vetoed by the National Football League because of GNC's placement on an NFLPA blacklist for selling products that contain substances banned by the NFL. The letter of intent claimed that Fox had not informed them of any such rules when they purchased the ad time, and cited that the purchase induced them to "spend millions of dollars in production costs and in the development of a national, coordinated marketing and rebranding campaign" around the commercial. The NFL itself does not prohibit ads for health stores unless they contain references to specific prohibited products; the GNC ad only contained motivational themes and no references to its products.
Sources: en.wikipedia.org
Reported activity is highest at MC4R, with lower potency at MC1R and MC3R. The MC4R interaction is generally treated as the most relevant to its central effects. Selectivity is not absolute, and activity across the family is dose-dependent.
Indirect evidence from animal studies supports central access, and the proposed mechanism requires it. Direct quantification in humans is limited. How much reaches specific brain regions remains an open question.
Published descriptions give a plasma half-life of roughly two to three hours after subcutaneous administration. Values vary with assay method and study population. The figure is an average rather than a fixed molecular property.
Purity is normally expressed as a percentage of total peak area from a chromatographic run. The value depends on the column, gradient and detection wavelength chosen. Results generated under different conditions are therefore not always interchangeable.