bremelanotide and Disease-Models--Animal

Melanocortinergic agents are currently being investigated for a possible therapeutic role in male and female sexual dysfunction. These investigations were sparked by findings that systemic administration of a synthetic analog of alpha-MSH, MT-II, causes penile erections in a variety of species, including humans. Several other melanocortinergic agents including HP-228, THIQ, and bremelanotide (PT-141) have since been shown to have erectogenic properties thought to be due to binding to melanocortin receptors in the central nervous system, particularly the hypothalamus. Bremelanotide, a nasally administered synthetic peptide, is the only melanocortinergic agent that has been clinically studied in both males and females. Data from Phase II clinical trials of bremelanotide support the use of melanocortin-based therapy for erectile dysfunction. Studies using animal models have demonstrated that pre-copulatory behaviors in female rats analogous to sexual arousal are evoked, and preliminary clinical data also suggest a role in promoting sexual desire and arousal in women. Based on bremelanotide clinical experience, administration of a melanocortin agonist is well tolerated and not associated the hypotension observed with phosphodiesterase-5 inhibitors currently used to treat erectile dysfunction. This review discusses investigations of melanocortin agonists for the treatment of sexual dysfunction with emphasis on proposed sites and mechanisms of action in the central nervous system that appear to be involved in melanocortinergic modulation of sexual function. Current research validates use of melanocortinergic agents for the treatment of both male and female sexual dysfunction.

Topics: alpha-MSH; Animals; Disease Models, Animal; Humans; Melanocortins; Peptides, Cyclic; Receptors, Melanocortin; Sexual Dysfunction, Physiological

Bremelanotide is an analogue of the naturally occurring peptide alpha-melanocyte-stimulating hormone (alpha-MSH). It stimulates erection in men and male rats, and is currently in clinical trials for the treatment of erectile dysfunction.. To review the effects of bremelanotide, an analogue of the naturally occurring peptide alpha-MSH, on the preclinical indices of sexual desire in female rats, and where in the brain these actions may occur.. Appetitive sexual behaviors, such as solicitations, hops and darts, and pacing, were assessed along with consummatory behaviors such as lordosis. The involvement of brain regions was assessed following direct administration to the region, by the stimulation of molecular markers of neural activation, and using microdialysis to examine extracellular fluid for different neurotransmitters.. Using a model that allows ovariectomized, hormone-primed female rats to control the timing of sexual encounters with males, we tested the ability of bremelanotide to increase appetitive (proceptive) and/or consummatory sexual behaviors.. Bremelanotide dramatically and selectively increased measures of solicitation in female rats, without altering pacing or lordosis, following both peripheral (subcutaneous) administration or infusions directly into the lateral ventricles or medial preoptic area (mPOA), but not the ventromedial hypothalamus. The mPOA is critical for the display of appetitive sexual behaviors in females and males of a variety of species. Peripheral administration of bremelanotide activates the mPOA and other hypothalamic and limbic regions of the brain involved in sexual behavior, and may work by activating dopamine terminals in the mPOA.. To the extent that solicitations indicate the desire of female rats to engage in sexual activity, bremelanotide appears to possess the behavioral, pharmacological, and neuroanatomical specificity required of a drug in the treatment of hypoactive sexual desire disorders.

Topics: alpha-MSH; Animals; Copulation; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Male; Orgasm; Peptides, Cyclic; Rats; Rats, Long-Evans; Sexual Dysfunction, Physiological