A study from NYU School of Medicine scientists has shown that a mother's instinct to gather wandering offspring is linked to the chemical released by brains called dopamine. The work was published in Neuron yesterday.
"Our study shows precisely how a maternal instinct is generated in the mammalian brain," says study senior investigator Dayu Lin, Ph.D., an assistant professor at the Neuroscience Institute at NYU Langone Health. "Moreover, we believe that the findings overturn the longstanding idea that the dopamine system produces a 'rush' after a good behavior, and argue instead that dopamine may drive actions before any satisfaction is felt."
In this study, the researchers studied a brain region called the medial preoptic area (MPOA) in dozens of female mice as they interacted with their own and others' pups. They found that cells that expressed a signaling protein called estrogen receptor alpha expressing (MPOA Esr1) were the ones that were most active during the gathering act and that the activity dropped once the mother finished.
The team chemically stimulated these cells in mothers and virgin mice, and both groups went to retrieve pups, even if they weren't theirs. When the chemical activity was blocked, the female mice no longer went to retrieve pups.
Looking at other areas of the brain, the researchers saw that axons of MPOA Esr1 reached the ventral tegmental area (VTA), where dopamine is produced. Previously, Lin and colleagues showed that when the chemical signaling to the VTA cells was blocked, retrieval behaviors were impaired. In this current study, they found that when MPOA Esr1 axons that reached the VTA were stimulated, mothers quickly went to retrieve their pups. Brain recordings in new mother mice confirmed these results.
The teams' future plans are to see what changes occur in the brains of mothers that sensitize them to their pups between pregnancy and lactation. They also plan to look to see what occurs in the brains of father mice, who are known to be less aggressive around the time of birth.