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Oxytocin was traced back to its unique receptor cells. There researchers found oxytocin controls the volume of "social information" being processed by individual neurons. Curbing so-called excitatory (inhibitory) signals Image Credit: Adapted from image by Logan Parsons, Nature Magazine

How oxytocin makes a mom

The oxytocin hormone teaches mom's brain to respond to her baby's needs. Future research could lead to using oxytocin as treatment for social anxiety, post-traumatic stress disorder and perhaps other brain behavioral issues as well.

Neuroscientists at New York University, Langone Medical Center have discovered how the powerful brain hormone oxytocin acts on individual brain cells to prompt specific social behaviors. The findings are published in the journal Nature April 15, 2015.

Until now, oxytocin — sometimes called the "pleasure hormone" — has been known for its role in inducing sexual attraction and orgasm, and regulating breast feeding and promoting maternal-infant bonding. But precisely how was not known.

"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 disorder, and even psychological issues from child abuse."

Robert Froemke PhD, Assistant Professor at New York University Langone, Skirball Institute of Biomolecular Medicine, and study senior investigator.

In mice, Dr. Froemke and his team mapped oxytocin back to unique receptor cells on the left side of the cortex. There they found that oxytocin controls the volume of "social information" being processed by individual neurons and curbing so-called excitatory (inhibitory) signals — the neurons immediately determinine how female mice with pups should respond to their cries for help and attention.

In separate experiments in female mice with no pups — and 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 nest. These females quickly learned to fetch 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 became permanent, researchers say; the mice with no offspring continued to retrieve pups even when their oxytocin receptors were later blocked.

Key to the researchers' efforts to track oxytocin as it worked in individual brain cells, was the use of an antibody. Developed at NYU Langone, the antibody specifically binds to oxytocin-receptor proteins located on each neuron. The antibody allowed the cells to be seen under a microscope.

"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."

Bianca Marlin PhD, lead study investigator and postdoctoral research fellow at New York University Langone

Abstract
Oxytocin is important for social interactions and maternal behaviour. However, little is known about when, where and how oxytocin modulates neural circuits to improve social cognition. Here we show how oxytocin enables pup retrieval behaviour in female mice by enhancing auditory cortical pup call responses. Retrieval behaviour required the left but not right auditory cortex, was accelerated by oxytocin in the left auditory cortex, and oxytocin receptors were preferentially expressed in the left auditory cortex. Neural responses to pup calls were lateralized, with co-tuned and temporally precise excitatory and inhibitory responses in the left cortex of maternal but not pup-naive adults. Finally, pairing calls with oxytocin enhanced responses by balancing the magnitude and timing of inhibition with excitation. Our results describe fundamental synaptic mechanisms by which oxytocin increases the salience of acoustic social stimuli. Furthermore, oxytocin-induced plasticity provides a biological basis for lateralization of auditory cortical processing.

Other researchers involved in the study, conducted entirely at NYU Langone, were Mariela Mitre, BE; James D'amour, BSc; and Moses Chao, PhD, whose laboratory developed the oxytocin receptor antibody used to track hormone activity.

Funding support for the study was provided by the National Institute on Deafness and Other Communication Disorders and the National Institute of Mental Health, both members of the National Institutes of Health. Corresponding grant numbers are DC009635, DC12557, and T32 MH019524. Additional funding was provided by McKnight and Pew scholarships; Sloan and NYU-Whitehead research fellowships; and a Skirball Institute collaborative research award.

For more information, go to:
http://skirball.med.nyu.edu/faculty/az/froemke-robert-c
http://froemkelab.med.nyu.edu/research
http://nature.com/articles/doi:10.1038/nature14402

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