Melanocortinergic Activation and Its Implications

Melanotan 2 is a synthetic version of the natural chemical melanocortin which is found in animals. This also mimics the effects of alpha-melanocyte stimulating hormone or a-MSH. The natural version of this chemical has been found to cause tanning of the skin as well as aphrodisiac effects in animals.

This peptide also appears to have effects in regulating food management or nerve reactions. Research on animal test subjects is still discovering the effects of this peptide on animals. To date, this peptide has not been approved for research on human test subjects.

Melanocortinergic Activation and Its Implications

Hypothalamic neurocircuitry, which is used to regulate energy homeostasis in rats, is not developed until the third postnatal week.
•    The fibers from hypothalamic arcuate nucleus are made up of a-MSH and neuropeptide fibers which are located in the brainstem as well as the melanocortin system. These can be noted in the receptor antagonists for malanoatn 2 by measuring NRP expression, body weight or energy expenditure.
•    Rat pups were injected with saline or melanotan 2 and then killed so their stomach weight and brown adiopose tissue could be measured for protein 1 mRNA uncoupling, could be compared after melanotan 2 administration.
•    Stomach weight was seen to decrease after the uncoupling of protein 1 mRNA.

These results were seen at all ages, which implies that a decrease food intake and increase in energy expenditure is standard. However, melanotan 2 was not found to affect NPY mRNA in the hypothalamus.

These effects were not shown to be mediated b NPY expression.

Promoting Peripheral Nerve Regeneration

Neuroprotective and neurotrophic potential of a-MSH analogsy, cyclo amide, a melanocortin receptor with known potency was examined.
•    Static nerve crush models were used to create a paradigm in order to investigate the neruotrophic properties associated with melanotan 2.
•    Melanotan 2 was found to significantly enhance the recovery of sensory function in these areas, after the sciatic nerve in rats suffered a crush lesion.

In addition to these results melanotan 2 was also found to possess potent neuroprotective properties. During the study application of melanotan 2 was found to partially protect these nerves from toxic neuropathy that was induced by cisplatin. This data was the first to demonstrate that a potent a-MSH analog, such as melanotan 2, can be effective in neuroprotection and regeneration.

Role in Central Control of Feeding

Injecting of melanocortin peptides or their analogues into cerebrospinal fluid or into ventromedial hypothalamus tissue in subnanomolar or nanomolar has been found to cause a long-term inhibition of an animal’s food intake.
•    These effects can remain in place for up to 9 hours. This phenomenon has been observed in several animal species, but it was most potent in rabbits. Anorectic effects of peptides were found to be primary rather than secondary to the shift of additional components of melanocortin-induced behaviors.
•    The site actions of the brain is not the effect adrenal mediation is exhibited in adrenalectomized animals. This is a strong effect because this inhibition did not reduce hunger induced by insulin induced hypoglycemia, 24 hour starvation or the stimulation of y-aminobutyric acid, opioid systems or noradregric.
•    Melanocortins appear to play a vital role in stress induced anorexia because in rats this condition is significantly attenuated by a blockage of receptors for melanocortin MC4.

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The physiological effects of this phenomenon, plus inhibitory properties of melanocortins and the subsequent consequences could cause body weight homeostasis in animals. This is showcased hyperphagia or obesity syndromes, causing mutations of melanocortin MC4 genes.

Clinical trials are focusing on discovering potential therapeutic effects of melanocortin, which focuses on further understanding of the function of these peptides.