March 21, 2025, 2:28 pm | Read time: 5 minutes
When we have sex, the body seems to take over. However, the real fireworks are ignited in the head. As more detailed knowledge about this has so far mainly been gained during the initiation of sex, this discovery by neurologists is a minor sensation: their study with mice during mating may reveal exactly what happens in the male brain during sex. The findings could lead to new treatment approaches for sexual dysfunction in the future.
Like many scientific fields, research into sexual behavior has historically overlooked women. There are several reasons for this, particularly in this field, where the individual phases of sexual intercourse are more readily measurable in men and male animals such as mice, rats, or primates commonly used in research. The ejaculation phase is clearly distinguishable from erection and penetration, with each phase marked by distinct physiological indicators. Moreover, these transitions are regulated by specific regions in the male brain. The female orgasm is more variable, context-dependent, and challenging to replicate in standardized experiments. Consequently, research into sexual behavior often focuses more on men than women, a trend that the latest study in this field continues. Nevertheless, it bridges a knowledge gap regarding what happens in the male brain during sex. To do this, the researchers analyzed the brain activity of mice during mating.
Overview
What Happens in the Femail and Male Brain During Sex?
In the past, many animal and human studies on sexual behavior and what happens in our brains during sex have focused on the initiation of sexual intercourse and the post-sexual phase. It is known which brain regions and neurotransmitters are responsible for this.
Recent studies on female sexuality, for example, show that dopamine also plays a role in women but that oxytocin and serotonin are possibly more important than in men.1 In men, for example, we know that dopamine in the brain’s reward system (nucleus accumbens) influences sexual motivation. The neurotransmitter is also crucial for sexual performance. After ejaculation, serotonin takes over in men.2
Studies show that the prefrontal cortex is shut down during female orgasm.3 In men, on the other hand, the ventral tegmentum and the nucleus accumbens are highly active during ejaculation.4 Both regions are associated with reward and dopamine.
Researchers Decode How the Brains of Male Mice Control the Path to Ejaculation During Sex
But what happens in between? How exactly does the male brain regulate the path to ejaculation? Researchers have not yet fully understood this. Ai Miyasaka and a team of researchers from the University of Tsukuba and the National Institute of Biological Sciences, Beijing, may have finally found out. Their findings have been published in the journal Neuron.5
The researchers investigated how two important neurotransmitters, acetylcholine and dopamine, interact in the brains of male mice during sexual intercourse with female mice. They found that these neurotransmitters work together in a rhythmic pattern to coordinate the different phases of sexual behavior. What is particularly interesting is that targeted manipulation of these signals can influence the probability of successful ejaculation.
How did the researchers measure whether and how acetylcholine and dopamine interact in the brains of mice during intercourse? The method for recording neuronal activity is called the FFP system (fused fiber photometry), which involves building light-sensitive switches into the nerve cells that make it possible to switch their activity on and off using light and thus draw conclusions about their function. Neurons and neuronal circuits can be precisely manipulated and researched in this way.6
What Exactly the Researchers Found Out
The new findings on the mechanisms in the brain that control male sexual behavior in detail:
- Before the mouse even gets to penetration, the brain begins to rhythmically release acetylcholine — a kind of “start signal.”
- As soon as the mouse begins penetration, dopamine comes into play. It follows a rhythm that corresponds exactly to the pelvic thrust rhythm.
- If acetylcholine or dopamine is artificially blocked, penetration or ejaculation is less likely to occur. This means that both substances are necessary for everything to work.
- If acetylcholine is increased during penetration, something surprising happens: The mouse climaxes immediately. At the same time, the dopamine frequency slows down, apparently a kind of “end signal” for the act.
- Computer models confirmed that this “double rhythm” is generated by a mutual regulation of acetylcholine and dopamine.
In a nutshell, acetylcholine gives the starting signal, dopamine provides the rhythm, and both together determine when it is over. Nothing works without this finely tuned exchange!
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What Do These Findings Tell Us? A Lot!
One might wonder: A study on the mating behavior of mice is intriguing, but how does it benefit humans, and specifically men? Clearly, further research is needed to determine whether the results can be transferred one-to-one to humans. Regardless, Miyakasa believes that her discovery could pave the way for potential sex therapies, among other applications. Given that acetylcholine seems to initiate ejaculation, targeted pharmacological interventions could provide new therapeutic options for men with premature or delayed ejaculation.
Other potential pharmaceutical applications relate to Parkinson’s disease, as patients with this condition frequently experience altered dopamine levels that can impact sexual function. The new findings could help to improve therapies for such accompanying symptoms. Dopamine also plays a role in psychiatric illnesses. The results could, therefore, also be important for research into anhedonia (lack of pleasure) or other pleasure disorders.