Abstract
In many species, ejaculation is followed by a state of decreased sexual activity, the post-ejaculatory refractory period. Several lines of evidence have suggested prolactin, a pituitary hormone released around the time of ejaculation in humans and other animals, to be a decisive player in the establishment of the refractory period. However, data supporting this hypothesis is controversial. We took advantage of two different strains of house mouse, a wild derived and a classical laboratory strain that differ substantially in their sexual performance, to investigate prolactin’s involvement in sexual activity and the refractory period. First, we show that there is prolactin release during sexual behavior in male mice. Second, using a pharmacological approach, we show that 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, respectively. Therefore, we show compelling evidence refuting the idea that prolactin released during copulation is involved in the establishment of the refractory period, a long-standing hypothesis in the field of behavioral endocrinology.
Highlights
In many species, ejaculation is followed by a state of decreased sexual activity, the postejaculatory refractory period
The post-ejaculatory refractory period (PERP) is highly conserved across species and includes a general decrease in sexual activity and inhibition of erectile function in humans and other primates[2]
We collected blood samples upon the execution of pre-determined, identifiable, behavioral events that correspond to different internal states of the male: before sexual arousal, at the transition from appetitive to consummatory behavior (MA, mount attempt, immediately after the male attempted to mount the female), during consummatory behavior, and after ejaculation (Fig. 1a, see “Methods” for details)
Summary
Ejaculation is followed by a state of decreased sexual activity, the postejaculatory refractory period. Several lines of evidence have suggested prolactin, a pituitary hormone released around the time of ejaculation in humans and other animals, to be a decisive player in the establishment of the refractory period. Removal of PRL-producing pituitary tumors or treatment with drugs that inhibit PRL release reverse sexual dysfunctions[25,26] Taking these observations into consideration, it has been hypothesized that the PRL surge around the time of ejaculation plays a role in the immediate subsequent decrease of sexual activity, the hallmark of the PERP. This idea is widespread in behavioral endocrinology textbooks[27] and the popular press (https://en.wikipedia.org/wiki/Refractory_period; https://www.humanitas.net/treatments/prolactin)
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