Orgasm men are capable of achieving them is supported by men who have reported having multiple, consecutive orgasms, particularly without ejaculation. Males who experience dry orgasms can often produce multiple orgasms, as the refractory period is reduced. An increased infusion of the hormone oxytocin during ejaculation is believed to be chiefly responsible for the refractory period, and the amount by which oxytocin is increased may affect the length of each refractory period. Another chemical which is considered to be responsible for the male refractory period is prolactin, which represses dopamine, which is responsible for sexual arousal. Because of this, there is
Melanin-concentrating hormone as part of the immune response. More research is needed to fully determine and understand any relationship between MCH and possible immune responses in skin. MCH was initially discovered in the teleost fish; it was found to help determine the fish's skin color. Later, a mammalian version of MCH was discovered in rats, where most of the functions and localizations are conserved across mammalian species. Melanin-concentrating hormone Melanin-concentrating hormone (MCH) is a cyclic 19-amino acid orexigenic hypothalamic peptide originally isolated from the pituitary gland of teleost fish, where it controls skin pigmentation. In mammals it is involved in the regulation