summary: A new study reveals how progesterone-responsive neurons in the ventromedial hypothalamus (VMH) switch between sexual receptivity and sexual rejection in female mice. These neurons are highly activated when the female is past fertile age and during male rejection behaviors such as kicking and boxing.
During fertility, these neurons receive inhibitory signals that reduce their activity and allow mating. Using advanced techniques like optogenetics, the researchers found that activating these neurons induces rejection even in fertile females, while silencing them reduces receptivity. It was confirmed that rejection behavior was reduced without causing it.
This dual neural system provides a robust mechanism to balance mating behavior based on internal states. This discovery may provide insight into human sexual behavior and disorders related to the hypothalamus.
important facts:
- Progesterone-responsive neurons in the anterior VMH drive sexual rejection behavior.
- These neurons switch their activity based on fertility, dynamically balancing mating behavior.
- Optogenetics confirms its role as a neural “switch” for rejection in female mice.
sauce: Champalimaud Unknown Center
Female mammals, such as rodents, only accept mating attempts during the breeding season and actively reject males outside of this period. While the brain regions that control sexual acceptance are well-studied, the mechanisms behind active rejection are less well-studied.
“Sexual rejection is not simply a lack of receptivity, but an aggressive behavior,” explains Susana Lima, senior author and head of the neurobehavioral laboratory at CF.
“Females engage in defensive behaviors such as running away from males, kicking, and boxing. We wanted to understand how the brain switches between these two very different behavioral states.”
The focus of their research is the ventromedial hypothalamus (VMH). The VMH is an evolutionarily ancient brain region that controls social and sexual behavior across species, including humans.
“Based on previous low-resolution imaging experiments showing VMH activity when accepting and rejecting male advances, we conclude that the VMH does not house a separate population of cells dedicated to rejection. “I thought,” Lima said.
The researchers focused on a little-studied area of the anterior VMH, specifically cells that respond to the hormone progesterone, which fluctuates throughout the reproductive cycle.
“These neurons are ideal for studying how women’s brains switch between acceptance and rejection during the cycle,” said lead author Nicholas Gutierrez-Castellanos.
No, yes. it depends.
“Understanding this inversion provides insight into how the brain integrates signals from the environment and the body to shape behavior,” continues Gutierrez-Castellanos.
“This is a striking example of how the same stimulus (in this case, an enthusiastic male) can cause completely opposite behaviors, depending on the female’s internal state.”
Through advanced techniques such as fiber photometry, which tracks real-time brain activity by measuring calcium signals, the researchers found that both receptive and non-receptive female mice were able to detect changes during interactions with males. The behavior of progesterone-sensitive neurons was observed.
The results were amazing. Anterior VMH neurons were highly active in nonreceptive females and correlated with defensive movements such as kicking and boxing, but were much less active in receptive females.
“Progesterone-responsive neurons in the anterior VMH appear to act as gatekeepers of sexual rejection,” says co-first author Basma Hussain.
“When a female is outside her reproductive capacity, these neurons become very active, causing a rejection response. However, during the breeding season, their activity decreases, allowing mating.”
Brain Dual Control Knobs
How do these neurons turn on or off depending on fertility? The researchers conducted electrophysiology experiments and measured the activity of progesterone-responsive neurons in brain slices.
“We found that in nonreceptive females, these neurons received more excitatory signals and were more likely to be activated,” Gutiérrez-Castellanos explains.
“Receptive females received more inhibitory signals and were less likely to fire. This proves how malleable and flexible the hypothalamus, and thus the brain’s neural connections, are. Masu.”
“The activity levels and excitation/inhibition balance of progesterone-responsive neurons in the pre-VMH strongly suggested a role for progesterone-responsive neurons in sexual rejection,” Hussain says.
“To confirm this, we used optogenetics to selectively activate these neurons with light.” Rejection behavior was induced. “It was like a switch was flipped. Even though the females were fertile, they acted as if they weren’t.”
Conversely, silencing these neurons in non-receptive women with chemicals reduced their rejection behavior, but interestingly did not make them completely receptive. This indicates that two distinct populations of neurons, one controlling rejection and the other controlling acceptance, work in concert. Generates appropriate behavior depending on the internal state of the woman.
“This setup gives the brain two ‘knobs’ to adjust,” Lima explains. “This is a more efficient and robust way for the brain to balance these behaviors, ensuring mating occurs when conception is most likely, while also preventing factors such as exposure to predators or disease that may interfere with mating. Minimize the risks and costs involved.”
Hussain added: “This dual system may add flexibility to the brain’s regulation of sexual behavior. Gender is not definitive; even in the receptive stage, females can still reject males. The ability to tap into both sets of neurons may enable more subtle and dynamic behaviors.”
Remarkably, these findings demonstrate that progesterone-responsive neurons in the posterior VMH that promote sexual receptivity undergo similar cycle-dependent changes, but in the opposite direction, being active during conception and This is consistent with recent studies showing that it is inactive outside of
“VMH is present in humans and likely plays a similar role,” Lima said.
“Recent studies in mouse models have shown that the VMH is altered in pathological conditions such as polycystic ovary syndrome. Furthermore, social isolation of female mice during development Changes in the same region may result in decreased sexual receptivity, highlighting the clinical relevance of VMH.”
“We are just beginning to scratch the surface of how the brain’s internal wiring coordinates social behavior,” Lima concludes.
“While there is still much to learn, these findings advance our understanding of how neural mechanisms and internal states drive complex social interactions, from sexual behavior to aggression and beyond.” It brings us one step closer.”
About this neuroscience research news
author: eddie young
sauce: Champalimaud Unknown Center
contact: Eddie Young – Champalimaud Unknown Center
image: Image credited to Neuroscience News
Original research: Open access.
“Hypothalamic node that periodically controls sexual rejection in womenWritten by Susana Lima et al. neuron
abstract
Hypothalamic node that periodically controls sexual rejection in women
Behavioral flexibility that depends on internal state, such as the ability to switch between rejecting or accepting sexual advances based on a woman’s reproductive potential, is important for maintaining meaningful social interactions.
Although the role of the ventrolateral ventromedial hypothalamus (VMHvl) in sexual acceptance is well established, the neural mechanisms underlying sexual rejection remain unexplored.
In this study, we identified neurons expressing progesterone receptors in the anterior VMHvl (aVMHvl).PR+) as a key regulator of cyclical female sexual rejection behavior.
in vivo Recordings revealed that these neurons were active during sexual rejection but not during sexual acceptance.
Slice electrophysiology shows that aVMHvlPR+ Receptive female neurons have a reduced balance of excitatory to inhibitory synaptic inputs.
Furthermore, activation and inhibition of aVMHvlPR+ Each neuron increases rejection in receptive females and decreases rejection in nonreceptive females.
Therefore, aVMHvlPR+ Neurons constitute an important neural substrate that controls female sexual behavior and provide an additional barrier to copulation when fertilization is not possible.
