Refractory period (sex) for treating sexual dysfunction. Sildenafil, used in the treatment of erectile dysfunction, was found in one scientific study to have caused "a decreased postejaculatory erectile refractory time (3.2 ± 0.7 vs. 6.4 ± 0.7 minutes)" in men diagnosed with premature ejaculation. It is additionally proposed that the gonadotropin inhibitory hormone (GnIH), which is considered to inhibit the hypothalamic-pituitary-gonadal axis and sexual functions causes refractoriness of the post-ejaculatory refractory period. This hypothesis also supports the increase of oxytocin and prolactin after orgasm in accordance with the previous studies. One alternative theory explains the male refractory period in terms of a peripheral
Social monogamy in mammalian species advantages, however, do not describe why monogamy, and not polygyny, has evolved in the species mentioned above. Some possible conditions which may account for cases of monogamous behavior in mammalian species may have to do with: There are several hypotheses for the evolution of mammalian monogamy that have been extensively studied. While some of these hypotheses apply to a majority of monogamous species, other apply to a very limited number of them. Vasopressin, a hormone that induces a male prairie vole ("Microtus ochrogasters") to mate with one female and stay by her side in order to protect her, has been