Oxytocin
Watching a mother mouse gather her pups into the family’s nest trains other female mice without pups to perform the same parenting task, a new study shows. Furthermore, these observations lead to the production of oxytocin in the brains of virgin female mice, biochemically shaping their maternal behaviors even before they have pups of their own.
Led by researchers at NYU Grossman School of Medicine, the new set of experiments involved round-the-clock filming of female mice interacting with their newborns as well as with virgin mice. Simultaneous electrical readings were made in several brain regions known to produce oxytocin or thought to be responding to the hormone. The research team built on its earlier studies of the so-called pleasure hormone showing that the release of oxytocin is essential not only for the onset of nursing but also for the initiating of other maternal behaviors.
Publishing in the journal Nature online Aug. 11, researchers describe what they called a never-before-seen behavior in which new mouse mothers would without prompting shepherd virgin female mice into the family’s nest along with their pups. Within 24 hours, the virgins began mimicking the maternal behavior of gathering the mom’s pups into the nest even if the mother was not there. Almost as quickly, virgin mice would also start to perform the pup-retrieving task without any direct contact with an experienced mouse mother and after having only “viewed” the mother through a clear plastic window.
The research team also measured brain electrical activity in virgin mice during shepherding and later when they became mothers on their own. They found that both the sight and sound of crying pups moved outside of their nest stimulated oxytocin production in a specific region of the brain, the hypothalamic paraventricular nucleus (PVN). By contrast, chemically blocking any of the visual, auditory, or oxytocin-producing PVN nerve pathways prevented virgin mice from learning to take care of pups.
“Our study shows that in mice the best way to be a mom is to watch and learn from an experienced mom,” says study senior investigator Robert Froemke, PhD, a professor in the Skirball Institute of Biomolecular Medicine at NYU Langone Health. “Given the evidence, we propose that similar mechanisms operate in human mothers.”
Froemke says the study findings in rodents add scientific evidence to the benefits observed from parenting classes in humans. He says the team next plans to examine if the same tutoring relationship exists among dad mice and virgin males.
“This work redefines oxytocin’s role in brain function, broadening its impact to include formidable and complex social networking activities that force the brain to pay attention and adapt to its surroundings at the time, whether it’s reacting to the sound of a pup’s cries or feelings of happiness,” says Froemke, who also serves as a professor in the departments of Otolaryngology-Head and Neck Surgery, and Neuroscience and Physiology at NYU Langone.
As part of the ongoing study, researchers analyzed nearly 5,000 hours (over six months) of video footage of several dozen mother mice interacting with their pups and with virgin mice.
Funding for the study was provided by NIH grants R01 HD088411, R01 DC12557, U19 NS107616, K99 MH106744, F32 MH112232, T32 MH019524, P30 CA016087, and P41 EB017183. Additional funding support was provided by Japan’s Strategic Program for Brain Sciences grant 16K15698; and scholarships from the McKnight Foundation, the Pew Charitable Trusts, and the Howard Hughes Medical Institute.
Besides Froemke, other NYU Langone researchers involved in the study include lead study investigator Ioana Carcea, MD, Ph.D. (now at Rutgers University in Newark, NJ); and study co-investigators Naomi Lopez Caraballo; Bianca Marlin, Ph.D.; Rumi Ooyama; Joyce Mendoza Navarro; Maya Opendak, Ph.D.; Veronica Diaz; Luisa Schuster; Maria Alvarado Torres; Harper Lethin; Daniel Ramos; Jessica Minder; Sebastian Mendoza; Chloe Bair-Marshall; Grace Samadjopoulos; Annegret Falkner, Ph.D.; Dayu Lin, Ph.D.; Adam Mar, Ph.D.; Youssef Wadghiri, Ph.D.; and Regina Sullivan, Ph.D. Other study co-investigators are Justin Riceberg, Ph.D., at the Icahn School of Medicine at Mount Sinai in New York City; Shizu Hidema, Ph.D.; and Katsuhiko Nishimori, Ph.D., at Fukishima Medical University in Japan; and Takefumi Kikusui, Ph.D.; and Kazutaka Mogi, Ph.D., at Azabu University in Kanagawa, Japan.