The short version of MC4R fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
Certificate of analysis documents usually report purity percentage, molecular weight, and appearance. Researchers verify identity by comparing observed and theoretical mass values. Chain-of-custody records and batch numbers help trace material from source to experiment. Independent verification of supplier claims is considered good practice when material identity is critical to a study. Records should include the storage history of each aliquot, and unexpected deviations in appearance or solubility warrant re-testing before use.
Lyophilized peptide material is generally stored at -20 °C or below to limit degradation, while reconstituted solutions are less stable and are typically kept refrigerated and protected from light. Repeated freeze-thaw cycles can accelerate aggregation and should be minimized. Stability for any specific lot depends on purity, moisture content, and packaging. Handling in a temperature-controlled environment reduces variability across replicates, and exposure to ambient humidity during weighing can introduce error. Aliquotting reduces the number of times a stock container is opened.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Cyclic heptapeptide | Synthetic analogue of alpha-MSH |
| Molecular formula | C50H68N14O10 | Acetate salt form commonly reported |
| Molecular mass | ~1025 Da | Monoisotopic value near 1025.2 |
| Key structural motif | Lactam bridge | Asp side chain to Lys side chain |
| Solid appearance | White to off-white powder | Lyophilised and hygroscopic |
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.
How receptor activation translates into a change in desire is not established in detail. Proposed steps include modulation of dopaminergic signalling in reward circuits and downstream effects on autonomic tone. Human data consist mainly of clinical trials measuring self-reported outcomes rather than direct measurements of brain activity or transmitter release. The transient rise in blood pressure sometimes observed after administration is likewise reported consistently but explained only partly by known melanocortin pathways.
Melanocortin receptors form a family of five G-protein-coupled proteins, labelled MC1R through MC5R, that respond to peptides derived from pro-opiomelanocortin. Alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone are the best-known endogenous ligands. The receptors are distributed differently across tissues, so a single agonist can produce effects in the brain, skin, adrenal gland and vasculature. This distribution explains why one peptide can influence both pigmentation and motivated behaviour.
Clinical development proceeded through two routes of administration. An intranasal formulation advanced first, but variable absorption and tolerability problems led to a switch to subcutaneous injection. The United States Food and Drug Administration approved the subcutaneous product in 2019 for hypoactive sexual desire disorder in premenopausal women. Marketing rights subsequently changed hands, and commercial availability has fluctuated since approval. Use in men, in postmenopausal women, and in combination with other agents remains outside the approved label.
Outside the approved product, bremelanotide circulates as a research chemical sold by peptide vendors, often labelled PT-141. Such material is not manufactured under pharmaceutical quality standards, and independent testing has repeatedly found content that differs from the label. Analytical certificates supplied with a purchase are not strong evidence of purity because they are usually generated by the seller. Online discussion tends to blur the distinction between the approved drug and unregulated powder, which complicates interpretation of reported experiences.
In November 1965 the government of the British colony of Southern Rhodesia issued an illegal Unilateral Declaration of Independence. This government represented the country's small white minority and was led by Prime Minister Ian Smith. The black majority of the population had little influence on the government, which sought to continue white racial privileges. At the time of independence the Rhodesian Security Forces were relatively large and well trained and equipped. Two groups with armed elements emerged as the opposition to the white Rhodesian regime. These were the Zimbabwe African National Union (ZANU), whose military wing was the Zimbabwe African National Liberation Army (ZANLA), and the Zimbabwe African People's Union (ZAPU) and its armed wing the Zimbabwe People's Revolutionary Army (ZIPRA). Both groups were initially based in Zambia, and from the late 1960s began dispatching insurgents into Rhodesia who used guerrilla tactics. These attacks initially proved ineffective and the Rhodesian military, which had been bolstered by forces from South Africa, was able to effectively counter them. Rhodesia's security situation began to deteriorate from late 1972, when the guerrilla armies began making more effective attacks in the north-east of the country. The collapse of the Portuguese Empire in 1975 that led to the independence of Mozambique led to a further increase to the challenges facing the Rhodesian regime, with the guerrillas using that country as well as Botswana as bases.
=== Superoxide stress response === When stressed under elevated levels of the superoxide radical anion O2−, bacteria respond by invoking the superoxide stimulon. Superoxide-generating compounds activate SoxR regulator by the one-electron oxidation of the 2Fe-2S clusters. Oxidized SoxR then induces the expression of SoxS protein, which in turn activates the transcription of structural genes of the SoxRS regulon.
=== Alternative pre-mRNA splicing generates multiple proteins from a single gene === The great majority of protein-coding genes encoded within the nucleus of metazoan cells contain multiple introns. In many cases, these introns were shown to be processed in more than one pattern, thus generating a family of related mRNAs that differ, for example, by the inclusion or exclusion of particular exons. The result of alternative splicing is that a single gene can encode a number of different protein isoforms that can exhibit a variety of (usually related) biological functions. Indeed, most of the proteins encoded by the human genome are generated by alternative splicing.
== Nearly defunct former casual restaurant chains == This list contains chains that were much larger in the past, with some having several hundred locations at their peak, which have since been reduced to a single location.
=== Amélie of Leuchtenberg === Amélie of Leuchtenberg (1812–1873) was Empress of Brazil as the wife of Emperor Pedro I (also King Pedro IV of Portugal). Between February and September 2012, researchers from the University of São Paulo exhumed her remains, along with those of Pedro I and his first wife, Maria Leopoldina. The investigation revealed that Amélie's body had been mummified, with her skin, hair, and internal organs preserved. Forensic examinations at the Hospital das Clínicas identified an incision in the jugular vein, used to inject aromatic substances such as camphor and myrrh during the original embalming. According to forensic archaeologist Valdirene Ambiel, the preservation was aided by the casket's hermetic seal, which prevented the growth of microorganisms. Before reinterment, the body was re-embalmed using methods similar to the original 19th-century process. The remains of Amélie, Pedro I, and Maria Leopoldina are interred within the crypt of the Monument to the Independence of Brazil in São Paulo.
Sources: en.wikipedia.org
Central obesity: waist ≥94 cm (37 in) men; ≥80 cm (31.5 in) women Dyslipidaemia: TG ≥2.0 mmol/L (177 mg/dL) and/or HDL-C <1.0 mmol/L (38.61 mg/dL) or treated for dyslipidaemia Blood pressure ≥140/90 mmHg or antihypertensive medication Fasting plasma glucose ≥6.1 mmol/L (110 mg/dL)
==== Homosexuality ==== Dr. Diana Fleischman, of the University of Portsmouth, and colleagues looked for a relationship between progesterone and sexual attitudes in 92 women. Their research, published in the Archives of Sexual Behavior found that women who had higher levels of progesterone scored higher on a questionnaire measuring homoerotic motivation. They also found that men who had high levels of progesterone were more likely to have higher homoerotic motivation scores after affiliative priming compared to men with low levels of progesterone.
Flutamide has been used to prevent the effects of the testosterone flare at the start of GnRH agonist therapy in men with prostate cancer. The combination of flutamide with an estrogen such as ethinylestradiol sulfonate has been used as a form of combined androgen blockade and as an alternative to the combination of flutamide with surgical or medical castration.
=== Influence on the Democratic Party === Analysts have suggested that Sanders's campaign shifted both the Clinton campaign and the Democratic Party politically leftward. A new political organization, Brand New Congress, was formed in April 2016 by former campaign staffers. It works to elect congressional representatives with platforms in line with Sanders. In August 2016, he formed Our Revolution, a political organization dedicated to educating voters about issues, getting people involved in the political process, and electing progressive candidates for local, state, and national office. Speaking on the PBS Newshour about the upcoming 2018 elections and discussing the main principles of the two major parties, Susan Page described the Republican Party as "Trump's party" and the Democratic Party as "Bernie Sanders's party", saying that "Sanders and his more progressive stance has really taken hold." Noting the increasing acceptance of his national single-payer health-care program, his $15-an-hour minimum wage stance, free college tuition, and many of the other campaign platform issues he introduced, an April 2018 opinion article in The Week suggested, "Quietly but steadily, the Democratic Party is admitting that Sanders was right." In July 2016, a Slate article called the Democratic platform draft "a monument to his campaign", noting not only his call for a $15 minimum wage but other campaign issues, such as Social Security expansion, a carbon tax, Wall Street reform, opposition to the death penalty, and a "reasoned pathway for future legalization" of marijuana.
Sources: en.wikipedia.org
== Data Utility == Differential refractometers are often used for the analysis of polymer samples in size exclusion chromatography. Other types of information that can be gathered from differential refractometers are:
== O == oligo - oligodeoxyribonucleotide - oligonucleotide - oligosaccharide-transporting ATPase - oncogene - oncovirus - open reading frame - operator - operon - origin of replication - ornithine(lysine) transaminase - osteomimicry
=== Impact of Coronavirus and CARES Act of 2020 === The COVID-19 pandemic in the United States impacted the economy significantly beginning in March 2020, as businesses were shut-down and furloughed or fired personnel. About 16 million persons filed for unemployment insurance in the three weeks ending April 9. It caused the number of unemployed persons to increase significantly, which is expected to reduce tax revenues while increasing automatic stabilizer spending for unemployment insurance and nutritional support. As a result of the adverse economic impact, both state and federal budget deficits will dramatically increase, even before considering any new legislation. To help address lost income for millions of workers and assist businesses, Congress and President Trump enacted the Coronavirus Aid, Relief, and Economic Security Act (CARES) on March 18, 2020. It included loans and grants for businesses, along with direct payments to individuals and additional funding for unemployment insurance. Some or all of the loans may ultimately be paid back including interest, while the spending measures should dampen the negative budgetary impact of the economic disruption. While the law will almost certainly increase budget deficits relative to the January 2020 10-year CBO baseline (completed prior to the Coronavirus), in the absence of the legislation, a complete economic collapse could have occurred. CBO provided a preliminary score for the CARES Act on April 16, 2020, estimating that it would increase federal deficits by about $1.8 trillion over the 2020-2030 period.
== Career == Fischbach was a junior fellow in the Department of Molecular Biology at Massachusetts General Hospital (2007–2009) before joining the faculty of the University of California, San Francisco in 2009. He moved to Stanford University as an associate professor in September 2017. As a Chan Zuckerberg Biohub Investigator, Fischbach is one of eight faculty members across Stanford, UCSF, and the University of California, Berkeley leading the CZ Biohub Microbiome Initiative, launched in 2018, with the goal of understanding how the microbiota can influence human health. Fischbach is currently a member of the scientific advisory board of NGM Biopharmaceuticals and a co-founder of Revolution Medicines.
=== Religion === Bukele's religious beliefs were controversial during his 2019 presidential campaign, with rumors that he was a Christian, a Muslim, or an atheist. The controversy began when pictures from 2011 of Bukele praying at a mosque with his father and brothers spread on social media. Bukele dismissed the controversy as an attempt by the political right to exploit Islamophobia in the predominantly Catholic country. Although Bukele does not identify with any religion, he has stated that he believes in God and Jesus. In a 2015 interview, Bukele said: "I am not a person who believes much in the liturgy of religions. However, I believe in God, in Jesus Christ. I believe in his word, I believe in his word revealed in the Holy Bible. And I know that God does not reject anyone because of their origins". Before that year, some Salvadorans believed that he was a Muslim. Bukele has referred to Bible verses, God, and Saint Óscar Romero — the archbishop of San Salvador who was assassinated in 1980 — in some of his speeches, and has called himself an "instrument of God" ("instrumento de Dios"). He met with Pope Francis in April 2015, saying that the pope told him that Rutilio Grande — a Jesuit priest who was assassinated in 1977 — would soon be beatified.
Sources: en.wikipedia.org
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.
The two compounds share the same cyclic core and are both non-selective melanocortin agonists. They differ chiefly at the C-terminus, where bremelanotide carries a free carboxylic acid and melanotan II a terminal amide.
Receptor binding profiles are well characterised in vitro, but the downstream pathway linking MC4R activation to behavioural effects is not fully mapped. Several intermediate neural circuits have been proposed without definitive confirmation.
Storage at -20 °C or below is standard for long-term stability. Desiccant and sealed containers limit moisture exposure. Solutions are prepared only when needed.