It could be that the key to being a better parent is all in your head, Harvard researchers say.
In a study in mice, Catherine Dulac, the Higgins Professor of Molecular and Cellular Biology and a Howard Hughes investigator, has pinpointed galanin neurons in the brain’s medial preoptic area (MPOA) that appear to regulate parental behavior. If similar neurons are at work in humans, it could offer clues to the treatment of conditions such as postpartum depression. The study is described in a May 15 paper published in Nature.
“If you look across different animal species, there are some species in which the father contributes to caring for the young — sometimes the work is divided equally, sometimes the father does most of the work — and there are species in which the father does nothing,” Dulac said. “The essential question is: Where is that variability coming from? We may be tempted to say that the mom has the neurons required to engage in parental behavior, and dads don’t — this paper shows that’s wrong.”
It’s long been known, Dulac said, that mice have highly stereotypical reactions to offspring. Among sexually experienced mice, both males and females build nests and groom and huddle with pups. Virgin females exhibit the same maternal behavior, while virgin males typically attack and kill pups.
Using genetic tools, graduate student Herbert Wu and other researchers in Dulac’s lab were able to activate galanin neurons in virgin males, and the results were startling.
Rather than attacking pups, the males immediately began to groom them. Other tests that killed the neurons resulted in parents that ignored the pups altogether or virgin females that behaved like males, attacking the pups.
Dulac and colleagues began exploring the roots of parenting behavior after making a surprising observation in the lab. Female mice lacking a functioning vomeronasal organ — which contains olfactory neurons responsible for certain innate behavior — suddenly behaved almost exactly like male mice.
“We came to the conclusion that what the VNO was doing in the female was repressing male-like behavior,” Dulac said. “If there is a repression of that behavior in females … we wondered if there might be a parallel system — if there are neurons in males that might drive female-like behavior, which normally are repressed.”
While the discovery of galanin neurons in the medial preoptic area suggests the answer is yes, it also raised other questions — particularly why the neurons would be present in males if they aren’t used.