Prolactin activates brain pathway promoting maternal caregiving behavior

New research has found a hormone is responsible for making mothers' interactions with newborns feel rewarding rather than just necessary.

The University of Otago – Ōtākou Whakaihu Waka study, published in Science Advances, looked at how a mother's brain changes to help her devote her energy to provide for the needs of her infant.

Co-lead author Dr Michael Perkinson, of the Department of Physiology, says they found an essential pathway in the brain switches on when a mother is interacting with her offspring.

In mice, it runs from a hormone sensing part of the brain into the brain's reward centre – which releases dopamine – and it's switched on by prolactin, a hormone essential for milk production that also surges after birth.

When we artificially activated this part of the brain, mice that had never had pups suddenly acted like devoted new mothers. When we blocked it in mothers, their normal surge of interest in pups didn't happen.

We know the brain's reward system gets rewired after birth to prioritise offspring, our findings help explain how that rewiring might happen, showing that prolactin acting through this specific pathway, tips the balance and makes time with a newborn feel rewarding rather than just necessary."

Dr. Michael Perkinson, co-lead author, Department of Physiology, University of Otago – Ōtākou Whakaihu Waka

Senior author Associate Professor Rosie Brown, also of the Department of Physiology, says the research is really helpful for mothers to understand why the way they think and feel changes so profoundly during pregnancy and after the birth of their child.

"The brain is undergoing remarkable change during pregnancy that really shapes the way we think and feel. It's not surprising that sometimes these changes can be difficult. Mothers and families need support and tools to positively shape this critical period of life," she says. 

The study builds on years of work from Otago's R. Brown Lab into how prolactin shapes a mother's brain and behaviour. The researchers hope their latest findings will feed into future research and development of treatments for mood disorders which are specifically tailored for pregnancy and for use during breastfeeding.

"Around one in five new mothers in Aotearoa New Zealand suffer from peripartum mood disorders. However, there are very little treatment options available for pregnant or postpartum mums that specifically target the cause of mood disruption during this time," Associate Professor Brown says.

"We are trying to understand how the brain is critically changing during pregnancy to bring about healthy changes in mood in mothers that enable them to thrive during this stage of life.

"By understanding how mood and behavior are regulated in mothers, we can target the cause of disrupted mood and effectively peripartum mood disorders."

Dr Perkinson hopes the research will help take some stigma away from parents who struggle to bond with their baby.

"It points to a brain pathway that isn't switching on as expected, not a personal failing."