If you have been reading about MC4 receptor 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 2025-12-29. Numbers and descriptions here follow the published literature rather than marketing material.
Identity and purity are established with orthogonal methods rather than a single test. Reverse-phase high-performance liquid chromatography with ultraviolet detection gives a purity figure by area normalization, while mass spectrometry confirms the expected molecular ion. Amino acid analysis or peptide mapping can detect sequence errors that a mass value alone would miss, and residual counterion content is sometimes measured separately. Common impurities include truncated sequences, oxidized residues, and deamidated products; reporting them individually is more informative than a single composite purity number.
Lyophilized peptide arrives as a white to off-white cake or powder and is normally held at minus twenty degrees Celsius or colder for extended periods. Short-term bench work at ambient temperature is tolerable for minutes, not hours, because the solid is hygroscopic and picks up moisture that promotes hydrolysis. Vials should stay in a desiccator or a sealed bag with desiccant, protected from light, since aromatic residues in the sequence are susceptible to photo-oxidation. Inventory records that note arrival date and storage location reduce the chance of using degraded material.
Reconstitution is usually performed with sterile water or a dilute acetic acid solution, and the choice of solvent affects both dissolution speed and final pH. Complete dissolution should be confirmed by visual inspection before any aliquot is taken, since undissolved particles can concentrate in the sampling volume. Repeated freeze-thaw cycles are the most common cause of gradual loss of purity, so dividing a stock into single-use aliquots at the first opportunity is standard practice. Working solutions kept refrigerated are generally used within days rather than weeks.
Early research on PT-141 grew out of work on melanotan II, a related cyclic peptide studied for pigmentation. Investigators observed that centrally acting melanocortin agonists also influenced sexual behaviour in animal models, and the programme shifted toward that endpoint. A nasal formulation was evaluated in clinical trials but showed inconsistent absorption, and later studies used subcutaneous administration instead. Regulatory approval in the United States followed in 2019 for a defined population of premenopausal women with acquired, generalised hypoactive sexual desire disorder. That approval was specific to that group rather than a broad indication.
Bremelanotide acts as a non-selective agonist at melanocortin receptors, with reported activity at MC1R, MC3R, MC4R and MC5R. The proposed basis for its central effects is activation of MC4R populations in the hypothalamus, a region associated with appetite and reproductive signalling. Because the peptide carries a net positive charge and polar side chains, it does not cross biological membranes freely, which is one reason oral administration is not the standard route. Effects generally appear within an hour of parenteral administration and are described as centrally mediated rather than peripheral.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized form |
| Solubility class | Soluble in water and DMSO | Dissolves readily |
| Typical storage temperature | -20 °C or lower | Long-term, desiccated |
| Standard purity method | Reverse-phase HPLC | Area normalization |
| Freeze-thaw guidance | Limit to three cycles | Aliquot in advance |
Evidence outside the studied population is sparse. Trials have concentrated on premenopausal women with a defined diagnosis, and data for postmenopausal women, men, and people taking interacting medications remain limited. Non-prescription use of the peptide for comparable goals is widespread but is not supported by published controlled data. Observed changes in blood pressure have drawn attention to cardiovascular monitoring during use. The literature generally frames the compound as a targeted receptor agonist rather than a general libido enhancer, and basic questions about mechanism and long-term safety are unresolved.
Bremelanotide functions as an agonist at several melanocortin receptor subtypes, with the strongest functional activity reported at the MC4 subtype. MC4 receptors sit in hypothalamic circuits that influence appetite, energy balance, and components of sexual behaviour. Rodents lacking functional MC4 receptors show altered mating behaviour, which supports a role for this pathway in desire. The precise sequence of events connecting receptor activation to reported human effects remains only partly characterised. Because the same receptor family governs pigmentation and inflammatory signalling, selectivity is a recurring theme in pharmacological discussion.
The compound emerged from a research programme examining melanocortin analogues for effects on skin pigmentation. During early human studies, participants reported spontaneous erections as an unexpected side effect, which redirected development toward sexual function rather than tanning. An intranasal formulation was investigated in clinical trials but did not reach market approval. A subcutaneous injectable version later completed the regulatory process, and the nasal route does not appear in approved labelling.
Approved use is narrow and jurisdiction-specific. In the United States, the injectable product is authorised for premenopausal women with acquired, generalised hypoactive sexual desire disorder, a diagnosis that requires documented distress. It is not approved for men, for postmenopausal women, or for use alongside hormonal contraceptives under the approved labelling. Outside regulated markets, the same peptide is frequently sold as a research chemical, where identity, purity, and sterility are not independently verified.
== Research == Magnesium sulfate has been used as an experimental treatment of Irukandji syndrome caused by envenomation by certain species of Irukandji jellyfish, but the efficacy of this treatment remains unproven.
August 5: The Partial Test Ban Treaty is signed by the US, UK and USSR, prohibiting the testing of nuclear weapons anywhere except underground. September 16: Malaysia was formed, with Tunku Abdul Rahman as its first prime minister. This was considered to have violated the Manila Accord because Malaysia was formed before the Sabah and Sarawak self-determination election results were reported. September 25: A border war was fought between Morocco and Algeria. October 14: The Aden Emergency begins against British rule. November 2: South Vietnamese President Ngo Dinh Diem is assassinated in a coup supported by the CIA. November 22: John F. Kennedy is shot and killed in Dallas. There has been some speculation over whether communist countries, or even the CIA, were involved in the assassination, but those theories remain controversial. Kennedy's vice-president Lyndon B. Johnson becomes President of the United States. December 12: Kenya becomes independent from the UK under Commonwealth status.
== General == The first sperm banks began as early as 1964 in Iowa, the United States, and Tokyo, Japan, and were established to support individuals who were infertile. As a result, over 1 million babies were born within 40 years. Sperm banks provide individuals who otherwise would not be able to conceive naturally the opportunity to have a child. This includes, but is not limited to, single women, same-sexed couples, and couples where one partner is infertile. In many parts of the world sperm banks are not allowed to be established or to operate. Where sperm banks are allowed to operate they are often controlled by local legislation which is primarily intended to protect the unborn child, but which may also provide a compromise between conflicting views which surround their operation. A particular example of this is the control which is often placed on the number of children which a single donor may father, which may be designed to protect against consanguinity. However, such legislation usually cannot prevent a sperm bank from supplying donor sperm outside the jurisdiction in which it operates, nor can it prevent sperm donors from donating elsewhere. There is a shortage of sperm donors in many parts of the world, and there is pressure from quarters for donor sperm from those willing and able to provide it to be made available as safely and as freely as possible.
=== EC 2.3.2: Aminoacyltransferases === EC 2.3.2.1: D-glutamyltransferase EC 2.3.2.2: γ-glutamyltransferase EC 2.3.2.3: lysyltransferase EC 2.3.2.4: Now classified as EC 4.3.2.9, γ-glutamylcyclotransferase EC 2.3.2.5: glutaminyl-peptide cyclotransferase EC 2.3.2.6: leucyltransferase EC 2.3.2.7: aspartyltransferase EC 2.3.2.8: arginyltransferase EC 2.3.2.9: agaritine γ-glutamyltransferase EC 2.3.2.10: UDP-N-acetylmuramoylpentapeptide-lysine N6-alanyltransferase EC 2.3.2.11: alanylphosphatidylglycerol synthase EC 2.3.2.12: peptidyltransferase EC 2.3.2.13: protein-glutamine g-glutamyltransferase EC 2.3.2.14: D-alanine γ-glutamyltransferase EC 2.3.2.15: glutathione γ-glutamylcysteinyltransferase EC 2.3.2.16: lipid II:glycine glycyltransferase EC 2.3.2.17: N-acetylmuramoyl-L-alanyl-D-glutamyl-L-lysyl-(N6-glycyl)-D-alanyl-D-alanine-diphosphoundecaprenyl-N-acetylglucosamine:glycine glycyltransferase EC 2.3.2.18: N-acetylmuramoyl-L-alanyl-D-glutamyl-L-lysyl-(N6-triglycine)-D-alanyl-D-alanine-diphosphoundecaprenyl-N-acetylglucosamine:glycine glycyltransferase EC 2.3.2.19: ribostamycin:4-(γ-L-glutamylamino)-(S)-2-hydroxybutanoyl-[BtrI acyl-carrier protein] 4-(γ-L-glutamylamino)-(S)-2-hydroxybutanoate transferase EC 2.3.2.20: cyclo(L-leucyl-L-phenylalanyl) synthase EC 2.3.2.21: cyclo(L-tyrosyl-L-tyrosyl) synthase EC 2.3.2.22: cyclo(L-leucyl-L-leucyl) synthase EC 2.3.2.23: E2 ubiquitin-conjugating enzyme EC 2.3.2.24: (E3-independent) E2 ubiquitin-conjugating enzyme EC 2.3.2.25: N-terminal E2 ubiquitin-conjugating enzyme EC 2.3.2.26: HECT-type E3 ubiquitin transferase EC 2.3.2.27: RING-type E3 ubiquitin transferase EC 2.3.2.28: L-allo-isoleucyltransferase EC 2.3.2.29: aspartate/glutamate leucyltransferase EC 2.3.2.30: L-ornithine Nα-acyltransferase EC 2.3.2.31: RBR-type E3 ubiquitin transferase EC 2.3.2.32: cullin-RING-type E3 NEDD8 transferase EC 2.3.2.33: RCR-type E3 ubiquitin transferase EC 2.3.2.34: E2 NEDD8-conjugating enzyme EC 2.3.2.35: capsaicin synthase EC 2.3.2.36: RING-type E3 ubiquitin transferase (cysteine targeting)
Sources: en.wikipedia.org
In an organic light-emitting diode (OLED), the electroluminescent material composing the emissive layer of the diode is an organic compound. The organic material is electrically conductive due to the delocalization of pi electrons caused by conjugation over all or part of the molecule, and the material therefore functions as an organic semiconductor. The organic materials can be small organic molecules in a crystalline phase, or polymers. The potential advantages of OLEDs include thin, low-cost displays with a low driving voltage, wide viewing angle, and high contrast and color gamut. Polymer LEDs have the added benefit of printable and flexible displays. OLEDs have been used to make visual displays for portable electronic devices such as cellphones, digital cameras, lighting and televisions.
Lieutenant Colonel James Edward Noel Bridgeman Shaw, Grenadier Guards, 559678; Brigade Major, Household Division, on the occasion of the Coronation of Their Majesties The King and The Queen. Nicholas Kester Smith, Director of Racing and Public Affairs, Ascot Racecourse. David William Courtenay Whelton, , Music Advisor, on the occasion of the Coronation of Their Majesties The King and The Queen. James Wyndham Williams, Music Advisor, on the occasion of the Coronation of Their Majesties The King and The Queen.
BIOCEV (Biotechnology and Biomedicine Centre of the Academy of Sciences and Charles University) is a joint research institute located in Vestec, Czech Republic. Established in 2015, it is operated by six institutes of the Czech Academy of Sciences (CAS) and two faculties of Charles University (Faculty of Science, Charles University and First Faculty of Medicine, Charles University). The center maintains collaborative ties with other institutions in the STAR cluster.
Other techniques for determining the dosage of CPA have validated this extrapolation, for instance affinity studies and prostatic CPA levels. The affinity of CPA for the AR is around 20-fold lower than that of DHT, and an excess of CPA levels of around 20 to 30 times those of DHT would hence be expected to maximally neutralize androgen signaling. In accordance, different publications have stated based on preclinical experiments that a 2- to 5-fold excess of CPA can inhibit the effects of testosterone by 50%, a 3- to 10-fold excess of CPA can reduce the effects of "potent androgens" (presumably testosterone and/or DHT) by 50%, and a 10-fold excess of CPA can inhibit the effects of testosterone by "almost 100%". High-dose CPA has been found to achieve prostatic levels that are at least 30-fold those of DHT. One study found that levels of CPA in the prostate gland in men being treated with 200 mg/day oral CPA were about 28 times those of DHT. In accordance with the preceding findings, it has been stated that oral doses of CPA of at least 300 mg/day may achieve a combined androgen blockade action in the treatment of prostate cancer. At a dosage of CPA of 100 mg/day in men with prostate cancer, circulating levels of CPA (e.g., 350 ng/mL) are on the order of 200-fold higher than circulating levels of testosterone (e.g., 100 ng/dL). In men who have undergone orchiectomy, 50 mg/day oral CPA results in a 500-fold excess of circulating CPA relative to circulating testosterone.
=== February === 2 February – Auckland Transport raises fares on buses, trains and ferries by 5.2% and ends the 10% off-peak discount. 3 February – The Tāhuna Glenorchy area of Central Otago is certified a Dark Sky Sanctuary, the 23rd such designation in the world and fifth in New Zealand. 4 February – 900 private sector laboratory workers strike to protest poor conditions and a lack of pay parity with their public sector counterparts. 5 February: The New Zealand Government confirms it will invest between NZ$100–150 million in upgrading State Highway 76 in Christchurch. It is announced that New Zealand's unemployment rate reaches 5.1%, the highest level since September 2020. Several Māori leaders and attendees protest against several government ministers including David Seymour, Paul Goldsmith and Shane Jones during a pōwhiri leading up to Waitangi Day. Seymour's speech is disrupted while Jones threatens to cut government funding to the Waitangi National Trust. 6 February: Prime Minister Christopher Luxon attends Waitangi Day celebrations at Ngāi Tahu's Ōnuku marae in Akaroa. The town hall in Roxburgh, Otago, which included the country's longest-running cinema, is destroyed by fire. The former building for New Zealand's sole Jewish school "Kadimah School" is vandalised with antisemitic graffiti referencing the Gaza war. 7 February: Health New Zealand chief executive Margie Apa resigns four months before the end of her contract. Taupō experiences heavy showers and thunderstorms, resulting in surface flooding and power outages.
Sources: en.wikipedia.org
Cold storage at minus twenty degrees Celsius or below is typical, with desiccant and protection from light. The solid form is far more stable than any solution.
Repeated freeze-thaw cycles, alkaline pH, and exposure to light or oxygen are the main drivers. Moisture uptake by the solid also matters.
Mass spectrometry provides the strongest single identity check by matching the observed molecular ion to the expected value. Chromatographic retention time alone is not sufficient.
PT-141 was the development code used for bremelanotide during its preclinical and early clinical programme. The peptide is now generally referred to by its international nonproprietary name.