"We came to the conclusion that what the VNO was going in the female was repressing male-like behavior," Dulac said. "If there is a repression of that behavior in femaleswe 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 MPOA suggests the answer is yes, it also raised other questions particularly why the neurons would be present in males if they aren't used.
What researchers found, Dulac said, is that those neurons, in fact, are used, but only after the male has mated, and they don't become fully active until three weeks the exact gestation period of mice pups - after mating occurs.
"The dad won't kill the pups after three weeks, because they may very well be his own offspring," Dulac explained. "Even if you remove males immediately after mating and segregate them from females, it's very striking half of them will behave paternally after three weeks. Simply mating seems to trigger some sort of clock, and that leads to paternal behavior."
Though it's not yet clear whether similar neural pathways exist in humans, researchers say galanin neurons are concentrated in a brain region responsible for many innate behaviors, such as feeding and sleep, and other neurons in the region have been shown to be conserved from mice across many mammal species, including humans.
"I would be extremely surprised if these neurons did not exist in humans," Dulac said. "What does that mean? It says that mothers can do it, and fathers can do it. What is really interesting, I think, is you now have an instinctive behavior and a very important social behavior and we have access to how it's being regulated."
Understanding how parental behavior is regulated, Du
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