In maternal female mice, aggression neurons show increased activity compared to virgin females, while mating neurons remain at a consistent activity level.

“The male mouse ceases from trying to mate with the female mouse and immediately tries to kill the female mouse.”

“And in mice, we discovered that there are male-specific neurons in VMH, and those neurons are activated during male aggression. Now, the neurons that are active in females when females fight in VMH are not sex specific, so they are also found in males. So this is already showing you some complexity, the male mouse VMH has both male-specific aggression neurons and generic aggression neurons. And then the female VMH, the mating cells are only found in females, they are female specific and not found in the male brain.”

“And so it turns out that if you measure the activity of the fighting and the mating neurons going from a virgin to a maternal female, the aggression neurons are very low in their activity in the virgin, but once the female has pups, the activation ability of those neurons goes way up and the mating neurons stay the same.”

“So we recently showed in a paper, this is work from one of my students, Mengyu Liu, that within VMH in females, there are two clearly divisible subsets of estrogen receptor neurons, and she showed that one of those subsets controls fighting and the other one controls mating. And in fact, if you stimulate the fighting-specific subset in a virgin, you can get the virgin to attack, which is something that we were never able to do before, and if you stimulate the mating one, you enhance mating.”

“So if you think of the balance between them like a seesaw, in the virgin, there is more activity in the mating neurons than in the fighting neurons, whereas in the nursing mother, there's more activity or more activation the other way around, the fighting neurons in the mating.”

“this sort of harks back to something we talked about earlier that the circuit for male sexual behavior is present in the female brain and he sort of identified a node in the female brain that lets them mate like males if he activates this optogenetically.”

“But um each awe a postdocctoral fellow in my lab when he was a graduate student uh activated a larger subset of these cells in the preoptic hypothalamus in the females and they all express estrogen receptor estrogen receptor alpha ESR1 and these females also mated like males.”

“When we finally identified the neurons in VMH that control aggression with a molecular marker, we found out that that marker was the estrogen receptor. Other labs have shown that the estrogen receptor in adult male mice is necessary for aggression. If you knock out the gene in VMH, they don't fight.”