Oxytocin, called the "love hormone" because it has been linked to social behaviors like cuddling, maternal care and pair bonding, is also necessary for female social interest during estrus.

A study Cell Press found oxytocin-responsive brain cells that are necessary for female social interest in male mice during estrus, the sexually receptive phase of their cycle. These neurons, found in the prefrontal cortex, may play a role in other oxytocin-related social behaviors such as intimacy, love, and mother-child bonding. 

Oxytocin-responsive neurons are found in many brain structures, highlighting the importance of the hormone for a variety of social behaviors. But it is not clear which cells are targeted by oxytocin, or how the hormone affects neural circuits.

One potential clue came when lead study author Miho Nakajima of The Rockefeller University discovered a population of neurons in the medial prefrontal cortex that express the oxytocin receptor. When the researchers disrupted the activity of these neurons, female mice lost interest in male mice during estrus and spent about the same amount of time with them as with a plastic Lego block.

By contrast, these females retained a normal level of social interest in other females during estrus, and in male mice when not in estrus. Moreover, the social behavior of male mice was unaffected by the silencing of these neurons.

"Our findings suggest that social interactions that stimulate oxytocin production will recruit this newly identified circuit to help coordinate the complex behavioral responses elicited by changing social situations in all mammals, including humans," says senior study author Nathaniel Heintz of The Rockefeller University. "Future investigation of the exact mechanisms responsible for activation of this interesting circuit may provide insights into autism spectrum disorder and other social behavioral disorders."

Taken together, the findings show that the new class of oxytocin-responsive neurons regulates an important aspect of female social behavior in mice. "Our work highlights the importance of the prefrontal cortex in social and sexual behaviors and suggests that this critical cell population may mediate other aspects of behavior in response to the elevated oxytocin levels that occur in a variety of different contexts," Heintz says.