SCI-TECH & AGRI

Not just a love hormone

Oxytocin, often referred to as “the love hormone,” is involved in a broader range of social interactions than previously understood, according to a study on mice that appears in the journal Nature.

The Stanford University School of Medicine discovery may have implications for neurological disorders such as autism, as well as for scientific conceptions of our evolutionary heritage.

Scientists estimate that the advent of social living preceded the emergence of pair living by 35 million years. The new study suggests that oxytocin’s role in one-on-one bonding probably evolved from an existing, broader affinity for group living.

The new study pinpoints a unique way in which oxytocin alters activity in a part of the brain called the nucleus accumbens, which is crucial to experiencing the pleasant sensation neuroscientists call “reward.” The findings not only provide validity for ongoing trials of oxytocin in autistic patients, but also suggest possible new treatments for neuropsychiatric conditions in which social activity is impaired.

“People with autism-spectrum disorders may not experience the normal reward the rest of us all get from being with our friends,” said senior author Robert Malenka. “So we asked, what in the brain makes you enjoy hanging out with your buddies?” Some genetic evidence suggests the awkward social interaction that is a hallmark of autism-spectrum disorders may be at least in part oxytocin-related. Certain variations in the gene that encodes the oxytocin receptor — a cell-surface protein that senses the substance’s presence — are associated with increased autism risk.

For this study, Malenka and lead author Glen teamed up to untangle the complicated neurophysiological underpinnings of oxytocin’s role in social interactions. They focused on the nucleus accumbens.

The group thinks their findings in mice are likely to generalise to humans because the brain’s reward circuitry has been so carefully conserved over the course of hundreds of millions of years of evolution. This extensive cross-species similarity probably stems from pleasure’s absolutely essential role in reinforcing behaviour likely to boost an individual’s chance of survival and procreation.

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