Prolactin stimulates male recovery time, indicating a study

If you enter a search engine – “why do men have to wait before they have sex again?” – you will quickly come across Prolactin. This little hormone is thought to be involved in hundreds of psychological processes in the body. These include the post-ejaculatory male recovery period. This period begins when a male ejaculates and ends when he regains his sexual potential.

If you examine a little more, you will see that this theory has even led to the development of so-called “remedies”. These promise to shorten a person’s recovery time by reducing the body’s prolactin levels.

Well, this is a bit of bad news for anyone who has bought products like that. A new study in mice by scientists at the Champalimaud Center for the Unknown in Portugal reveals that prolactin may not be the culprit after all. These results were published today (January 4) in the journal Communication Biology.

The theory

Ironically, the research project that ended up rejecting the theory did not aim to do so.

“When we started working on this project, we went to study the theory,” reminds us of Susana Lima, the lead researcher who led the study. “Our goal was to study more detailed the biological mechanisms by which prolactin could generate the recovery period. “

What is the basis of the theory? According to Lima, he appeared through several lines of evidence.

For one, some studies have shown that prolactin is released around the time of ejaculation in humans and rats. And since the recovery period begins right after ejaculation, prolactin seemed like a good candidate.

Also, extremely high levels of prolactin are associated with reduced sexual drive, anorgasmia and ejaculatory dysfunction. Finally, treatment with drugs that inhibit prolactin release in conditions of high prolactin is harmful, reversing sexual dysfunction.

“All of these different results point to a key role for prolactin in the elimination of male sexual behavior,” Lima says. “However, a direct link between prolactin and post-ejaculatory male recovery time has not been directly revealed. However, this theory has become so widespread that it is now appearing in textbooks as well as in the news media. “

Why not prolactin?

How did the team end up finding out that the theory was wrong?

To investigate the role of prolactin in the male rescue period, Lima and her team performed a series of experiments in mice.

“We chose mice as our model animal because the sequence of sexual behavior in mice is very similar to that of humans,” explained Susana Valente, the first author in the study. “Also, with mice, we can test different sequences that display different sexual performance, which makes the data richer. In this case we used two different sequences. One who has a short rescue, and another who has a long one, who lasts several days. “

The team began by examining whether prolactin levels also increase during sexual activity in male mice. “We measured the levels at the different levels of sexual behavior using blood samples. And sure enough, they increased dramatically during sexual interaction,” Valente said.

Once this side effect was determined, the researchers moved on to investigate the link between prolactin and the duration of the animals’ rescue.

Our first treatment was to artificially increase prolactin levels before the animals became sexually aroused. In particular, we made sure that the artificial levels matched those we measured during natural sexual behavior. If prolactin is indeed responsible for the recovery period, then the sexual activity of the animals should be reduced. “

Susana Valente, First Study Author, Champalimaud Center for the Unknown

Surprisingly, this treatment had no effect on the sexual behavior of the mice. “Despite the increase in prolactin levels, both sets of mice are mostly involved in sexual behavior,” she recalls.

Next, the researchers turned to see if blocking prolactin would have the opposite effect on the recovery time. In other words, if prolactin-free animals were more sexually active. Again, the answer was “No”.

“If prolactin was indeed essential for the duration of the incubation period, men without prolactin should have regained sexual activity after ejaculation faster than controls,” Valente says. “But they didn’t.”

Back to the drawing board

Together, the results of Valente and Lima provide strong evidence for the theory that prolactin stimulates the male recovery period. However, there is no doubt that prolactin is part of male sexual behavior. What part could it play?

“There are a lot of opportunities,” Lima said. “For example, there are studies that identify a role for prolactin in establishing parental behavior. It is also important to note that prolactin dinamics are very different in male and male mice. In mice, prolactin levels rise during courtship, but in men prolactin is unlikely to be released around ejaculation, and only when ejaculation is achieved. differences in his role across species. “

So why do men have to wait before round two?

“Our results show that prolactin is very likely to be to blame,” says Lima. “Now we can move on and try to find out what’s really going on”, she concludes.