How Oxytocin Switches On Maternal Behaviour

The mechanism by which the powerful brain hormone oxytocin acts on individual brain cells to prompt specific social behaviors has been uncovered by neuroscientists at NYU Langone Medical Center. The findings that could lead to a clearer understanding of how oxytocin and other hormones might be used to treat behavioral problems due to disease or traumatic brain injury.

Up until now, oxytocin (sometimes known as the “pleasure hormone”), has been better known for its role in inducing couples bonding, regulating breast feeding and promoting maternal-infant bonding. But its exact methods for controlling social behaviors were not known.

According to senior investigator Robert Froemke, PhD, an assistant professor at NYU Langone and its Skirball Institute of Biomolecular Medicine:

“Our findings redefine oxytocin as something completely different from a ‘love drug,’ but more as an amplifier and suppressor of neural signals in the brain. We found that oxytocin turns up the volume of social information processed in the brain. This suggests that it could one day be used to treat social anxiety, post-traumatic stress disorder, speech and language disorders, and even psychological issues stemming from child abuse.”

Social Information Volume Control

In experiments in mice, Dr. Froemke and his team mapped oxytocin to unique receptor cells in the left side of the brain’s cortex. They found that the hormone controls the volume of “social information” processed by individual neurons, curbing so-called excitatory or inhibitory signals, and immediately determining how female mice with pups responded to cries for help and attention.

Separate experiments looked at adult female mice with no pups, and therefore no experience with elevated oxytocin levels.

Adding extra oxytocin into their “virgin” brains led these mice to quickly recognize the barely audible distress calls of another mother’s pups recently removed from their home nest. These adult mice quickly learned to set about fetching the pups, picking them up by the scruffs of their necks and returning them to the nest, all as if they were the pups’ real mother.

This learned behavior was permanent, researchers say; the mice with no offspring continued to retrieve pups even when their oxytocin receptors were later blocked.

Said lead study investigator Bianca Marlin, PhD, a postdoctoral research fellow at NYU Langone:

“It was remarkable to watch how adding oxytocin shifted animal behavior, as mice that didn’t know how to perform a social task could suddenly do it perfectly.”

Vital to the researchers’ efforts to track oxytocin at work in individual brain cells was use of an antibody developed at NYU Langone that specifically binds to oxytocin-receptor proteins on each neuron, allowing the cells to be seen with a microscope.

“Our future research includes further experiments to understand the natural conditions, beyond childbirth, under which oxytocin is released in the brain,” Dr. Froemke adds.

Reference:

Bianca J. Marlin, Mariela Mitre, James A. D’amour, Moses V. Chao, Robert C. Froemke.
Oxytocin enables maternal behaviour by balancing cortical inhibition.
Nature, 2015; DOI: 10.1038/nature14402

Photo: Anthea Sieveking , Wellcome Images, Creative Commons by-nc-nd 4.0