In neuroscience, studying the impact of a molecule on behavior usually involves either adding or taking away the required molecule and observing the results. In this study, the role of oxytocin on maternal behavior was observed. Can a single hormone be responsible for the complex and varied reactions that we associate with motherhood?

When we speak about maternal behavior we automatically think of the protection and care that a mother gives her infant, behavior which is essential for many species for the survival of offspring. In this case, neuroscientists from NYU's Langone Medical Center studied the role of oxytocin on maternal behavior. Oxytocin is a hormone produced in the hypothalamus which regulates breast feeding, promotes maternal infant bonding, and induces sexual attraction and orgasm.

Fortunately (or unfortunately depending on who you ask!), due to strict legal restrictions it is not possible to inject substances into the human brain, and mice were chosen for the research, including female mice with pups.

By injecting ocytocin into the brains of adult female mice with no pups – and hence no experience with elevated oxytocin levels - the researchers were able to watch their behavior in the presence of another mother's pups. The mice quickly recognized the barely audible distress calls of the pups and set about 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. “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,” remarked Bianca Marlin, a post-doctoral research fellow.

One of the keys to the researcher's efforts to track oxytocin at work in the individual brain cells of mice, was the use of an antibody that specifically binds to oxytocin–receptor proteins on each neuron, allowing cells to be seen with a microscope. They found that the hormone controls the volume of social information processed by the brain, determining how female mice with pups responded to cries for help and attention.

This suggests that oxytocin could one day be used in the treatment of anxiety or post-traumatic stress disorder, and further research in planned. “Our future research includes further experiments to understand the natural conditions, beyond childbirth, under which oxytocin is released in the brain,” said Dr Froemke.