The short version of melanocortin receptor fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-09-23. Anything still debated is marked as such rather than presented as settled.
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
The material is commonly handled as a lyophilized powder in sealed vials. The solid dissolves readily in water and in polar organic solvents, producing a clear solution after reconstitution. Light, heat and repeated freeze-thaw cycles are the concerns most often raised in handling guidance, because peptide bonds and the constrained ring can degrade. Working solutions are generally prepared fresh, and material left in solution is treated as less stable than the dry form. These properties shape how laboratories store and aliquot reference material.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography with ultraviolet detection, often paired with mass spectrometry. Retention time supports identity, while the mass spectrum confirms the molecular weight of the intact peptide. Purity is frequently reported as a percentage of total peak area, a figure that depends on the wavelength, column and gradient used. Impurity profiling may also look for truncated sequences, oxidised forms and residual counterions. Amino acid analysis and peptide mapping provide orthogonal confirmation when required.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms add to total mass |
| Molecular mass | About 1024 daltons | Calculated for the free base |
| Structural class | Cyclic heptapeptide | Contains D-phenylalanine and norleucine |
| Parent hormone | Alpha-melanocyte-stimulating hormone | Endogenous tridecapeptide of 13 residues |
| Receptor profile | Non-selective melanocortin agonist | Interacts with MC1R, MC3R, MC4R and MC5R |
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan II holds no marketing authorisation from the Food and Drug Administration, the European Medicines Agency, the UK Medicines and Healthcare products Regulatory Agency or Australia's Therapeutic Goods Administration. Products sold under that name are treated as unapproved new drugs, and their sale or import is prohibited in several jurisdictions. Other countries classify the peptide as a prescription-only medicine or place it among controlled substances, so the legal position changes with the destination market. No pharmacopoeial monograph supplies an official specification, because the material is not a licensed pharmaceutical. Consequently, products offered online are not manufactured to a shared public standard.
The peer-reviewed record is dominated by small early-phase studies, case reports and pharmacovigilance summaries rather than large randomised trials. Papers typically examine tanning response, receptor selectivity or patterns of reported adverse events. Many note that participants obtained the peptide outside a clinical setting, which limits verification of composition and administered amount. Reported events vary widely, and causality is frequently unclear because the identity and purity of self-sourced material are unknown. Open questions include whether repeated melanocortin receptor stimulation produces cumulative effects, and how often label claims match actual content.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, which separates the target peptide from truncated or oxidised impurities. Mass spectrometry, most often coupled to liquid chromatography, confirms molecular mass and detects substitutions that chromatography alone may miss. Amino acid analysis and peptide mapping supply additional structural evidence, while nuclear magnetic resonance is reserved for full structural confirmation. Laboratories that examine samples sold online report wide variation in actual content, with some vials containing little or none of the labelled material.
Melanotan-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes remains an open question.
== Pharmacology: Pharmacodynamics/Mechanism of Action(MOA) == Synthetic cannabinoids act as Synthetic Cannabinoid Receptor Agonists (SCRA) by binding to cannabinoid receptors CB1 and CB2 . Its binding towards CB1 receptor will lead to receptor phosphorylation that recruits β-arrestin 1 and β-arrestin 2, resulting in a loss of responsiveness and internalization (endocytosis of molecules by the cell). Stimulation of CB1 receptor causes the dissociation of the βγ subunits of pertussis toxin-sensitive G proteins (Gi /Go) from the α subunit (Giα) which then contributes to acute inhibition of synaptic neurotransmitter release. β-arrestin can also stimulate the mitogen-activated protein kinase, thus inducing additional cellular effects. Synthetic cannabinoids can also bind to receptors other than CB1 and CB2 to activate inotropic transient receptor potential channels for cell membrane depolarization and Ca2+ influx.
O-GlcNAc is generally a dynamic modification that can be cycled on and off various proteins. Some residues are thought to be constitutively modified by O-GlcNAc. The O-GlcNAc modification is installed by OGT in a sequential bi-bi mechanism where the donor sugar, UDP-GlcNAc, binds to OGT first followed by the substrate protein. The O-GlcNAc modification is removed by OGA in a hydrolysis mechanism involving anchimeric assistance (substrate-assisted catalysis) to yield the unmodified protein and GlcNAc. While crystal structures have been reported for both OGT and OGA, the exact mechanisms by which OGT and OGA recognize substrates have not been completely elucidated. Unlike N-linked glycosylation, for which glycosylation occurs in a specific consensus sequence (Asn-X-Ser/Thr, where X is any amino acid except Pro), no definitive consensus sequence has been identified for O-GlcNAc. Consequently, predicting sites of O-GlcNAc modification is challenging, and identifying modification sites generally requires mass spectrometry methods. For OGT, studies have shown that substrate recognition is regulated by a number of factors including aspartate and asparagine ladder motifs in the lumen of the superhelical TPR domain, active site residues, and adaptor proteins. As crystal structures have shown that OGT requires its substrate to be in an extended conformation, it has been proposed that OGT has a preference for flexible substrates.
Arboreal animals frequently have elongated limbs that help them cross gaps, reach fruit or other resources, test the firmness of support ahead and, in some cases, to brachiate (swing between trees). Many arboreal species, such as tree porcupines, silky anteaters, spider monkeys, and possums, use prehensile tails to grasp branches. In the spider monkey, the tip of the tail has either a bare patch or adhesive pad, which provides increased friction. Claws can be used to interact with rough substrates and reorient the direction of forces the animal applies. This is what allows squirrels to climb tree trunks that are so large to be essentially flat from the perspective of such a small animal. However, claws can interfere with an animal's ability to grasp very small branches, as they may wrap too far around and prick the animal's own paw. Frictional gripping is used by primates, relying upon hairless fingertips. Squeezing the branch between the fingertips generates frictional force that holds the animal's hand to the branch. However, this type of grip depends upon the angle of the frictional force, thus upon the diameter of the branch, with larger branches resulting in reduced gripping ability. To control descent, especially down large diameter branches, some arboreal animals such as squirrels have evolved highly mobile ankle joints that permit rotating the foot into a 'reversed' posture. This allows the claws to hook into the rough surface of the bark, opposing the force of gravity.
Sources: en.wikipedia.org
"On January 22, the perverse Brown woke up anchored near the mouth of the Rimac River with the greatest insolence imaginable, as if he knew that there was no gunboat or armed ship in the port. His forces were composed of four ships and a pailebot. Three of them went ahead until they anchored in the same bay, fired a few cannon shots as if to mock them, they were answered by the castles, they raised anchor again and kept looking around until midnight, when they returned to shoot at the port, and They managed to do the damage by sinking one of the ships that remained at anchor, the frigate Fuente-Hermosa." Such was the hostility of the Argentine corsairs towards the Peruvian population, that it has been recorded that several travelers from Peru to Europe (especially friars of the Catholic Church), at the moment of undertaking the return from the Brazilian coast to Peru, arrived in to prefer the land route, from Goiás and Mato Grosso, to reach Peru via the Amazon, "rather than run the risk of falling into the hands of corsairs from La Plata at sea." On the other hand, some historians, with indigenist, Hispanist or revisionist orientations of the nationalist current, have wanted to affirm that the Argentine Liberator himself, Don José de San Martin, could have been an anti-Peruvian figure, questioning whether a foreigner would arrive (San Martín) to proclaim independence.
== Other uses == lh (digraph), in many languages Bristol LH, a type of British bus manufactured between 1967 and 1982 Chrysler LH platform, a type of Chrysler car made from 1993 through 2004 Late Helladic, a period in the history of ancient Greece, during the Bronze Age Leasehold, or tenure, in property law Left-handed, or left hand Letterhead, a heading at the top of a sheet of letter paper Lewis Hamilton (born 1985), British racing driver
== Contraindications == Contraindications of tiagabine include hypersensitivity (drug allergy) to tiagabine or its ingredients and severe hepatic impairment. The drug should be avoided in pregnant and nursing women.
Sources: en.wikipedia.org
=== Nonspecific zones === In these zones, the skin is similar to normal-haired skin and has the normal high density of nerves and hair follicles. These areas include the sides and back of the neck, the inner arms, the axillae (armpits) and sides of the thorax (chest).
Trails has been praised for its character arcs and worldbuilding, with its scope and sense of continuity being compared to the A Song of Ice and Fire novels by George R. R. Martin, the Forgotten Realms setting for Dungeons & Dragons, and the Marvel Cinematic Universe. Despite the series' English localization being praised for their quality, their slow release pace has been criticized, with them tending to lag years behind the original Japanese games. The music written for the series by Falcom Sound Team jdk, the company's team of composers, has also been praised. Characters or other elements from Trails have been featured in crossover promotions with other games, including Monster Hunter Frontier G, Chain Chronicle V, Dead or Alive 5, Fantasy Earth Zero, Langrisser Mobile, Utawarerumono: Zan, Valkyrie Anatomia, and a few Japanese mobile games. Characters from the series were also featured in a 2019 collaboration event with VREX, a virtual reality game arcade and café in Japan. As of 2021, a list of Trails characters was the largest article on the Japanese Wikipedia at over 440,000 characters. As of 2025, the series had sold nine million copies worldwide.
According to Mediapart, the text was "mostly relayed by far-right activists, press outlets or personalities". Dora Moutot and Marguerite Stern later launched "femellism", a movement which according to Arrêt sur images is rejected by many feminists "for its transphobia". According to its report, the movement adheres to conspiracy theories about the "funding of the trans lobby" and remains close to ultraconservative and far-right ideology. The two activists rejected these accusations and characterized femellism as a fight "against the oppressions that women suffer because of their sex". Libération criticizes the two activists for ideological connections and common obsessions with the activists of La Manif pour tous and the far-right. Marguerite Stern later lent her support to a well-known figure of the far-right, Julien Rochedy, a masculinist and former national director of National Rally's youth group between 2012 and 2014. In September 2024, she gave a lecture at the Institut de sciences sociales économiques et politiques, a group founded by Marion Maréchal, a far-right political figure. Dora Moutot and Marguerite Stern were welcomed shortly after by LREM deputies Caroline Yadan and Aurore Bergé, which led to protests from two other LREM elected officials, Pierre Karleskind and Raphaël Gérard, the latter denouncing Carloine Yadan's "vocabulary which makes echo of the hateful speeches heard in Poland or Hungary". Shortly after this meeting Aurore Bergé tabled an amendment to remove language inclusive of trans men from a bill designed to enshrine access to abortion.
Sources: en.wikipedia.org
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.
Melanotan-1, also called afamelanotide, is a linear analogue with greater selectivity for MC1R and has received approval in some jurisdictions for a specific photosensitivity disorder. Melanotan-2 is cyclic, less selective, and reaches central receptors more readily. The two are often confused in online discussion despite different pharmacology and regulatory status.
Alpha-MSH is an endogenous tridecapeptide derived from pro-opiomelanocortin. Melanotan-2 reproduces its core receptor-binding sequence inside a shortened, stabilised ring. The result is a molecule with a longer effective half-life and higher potency than the parent hormone.
The dry powder is more stable during transport and storage than a solution. It also allows a known amount of material to be reconstituted at a chosen concentration.