You may (or may not) have wondered why males are unable to have sex again straight after having sex, while females do not have this problem. Well even if you are in the "not interested" category, there are enough people out there who are interested that theories have been developed and products pedaled that promise to cut the time down to a minimum. Turns out everybody is in a hurry. One common thing that will come up if you are so inclined to Google “why do men have to wait before having sex again?” is the hormone Prolactin. Prolactin is a hormone that has been thought to be behind the post-ejaculatory refractory period (the scientific and least sexy way of saying the part after sex where it's impossible to go again). If you do some more searching, you'll probably be able to find treatments that claim to be able to inhibit Prolactin. While supplements to increase Prolactin might improve your milk supply during breastfeeding and may help if you want to enlarge your breasts, it looks like you might want to rethink treatments to reduce Prolactin if you're attempting to decrease your "downtime", so to speak. A team of scientists at the Champalimaud Centre for the Unknown in Portugal were originally attempting to explore the biological mechanisms by which Prolactin is responsible for the refractory period. The hormone is released in both rats and humans around the time of ejaculation, and abnormally high levels of it are associated with decreased sex drive, so it was logical to assume it had some role. “These different results all point towards a central role for prolactin in suppressing male sexual behaviour”, Dr Susana Lima, the principal investigator who led the study said in a press release. “However, a direct link between prolactin and the male post-ejaculatory refractory period was never directly demonstrated. Still, this theory has become so widespread that it now appears in textbooks as well as in the popular press." However, after investigating the link in experiments on mice, the team ended up finding that it might not be behind the phenomenon at all. “Our first manipulation was to artificially increase prolactin levels before the animals became sexually aroused. We specifically made sure that the artificial levels matched those we measured during natural sexual behaviour. If prolactin was indeed the cause of the refractory period, the animals’ sexual activity should have decreased”, first author of the study Susana Valente said. This, as the study published in the journal Communications Biology explains, did not happen. "Acute manipulations of prolactin levels, either mimicking the natural release during sexual behavior or inhibiting its occurrence, do not affect sexual activity or shorten the refractory period," the team wrote in their study. The team believe that the study offers strong counter-evidence to the idea that prolactin is behind the refractory period. Mice were chosen given their similarity in their sequence of sexual behavior to that of humans. Though they can't rule out that the role of the hormone may be different across species, they are confident that something else may be at play. “Our results indicate that prolactin is very unlikely to be the cause”, Lima added. “Now we can move on and try to find out what’s really happening." Source
