Missouri Southern State Southern University1, Biology, Joplin, MO 64804 Emory University2, Psychiatry, Atlanta, GA 30303
The neurohormone oxytocin (OT) plays a role in social bonding across a variety of species. Oxytocin regulates the attachment of the mother to her offspring by motivating her to adopt nurturing behaviors. However, the role of oxytocin in the infant has not been thoroughly explored. Social contact stimulates the release of oxytocin in adult rodents, thus we conducted two experiments to explore the relationship between maternal tactile stimulation and OT neuronal activation in neonatal prairie voles. In the first experiment, we investigated the ontogeny of the OT neurons in the hypothalamus. OT immunoreactivity (IR) was examined using an OT antibody directed against the n-terminus of the mature OT peptide. We then compared the density and distribution OT expression in the prairie vole brain at various stages of development ranging from embryonic to postnatal. In the second experiment, male and female vole pups on postnatal days 2-4 (PND 2-4) received simulated grooming with a paintbrush. One hour later, the brain was removed and IR was tested using double-labeled fluorescent immunohistochemistry for the immediate early gene, early growth response 1 protein (EGR1), and OT to identify activation of OT neurons in the PVN. In the first experiment, OT was present embryonically and OT containing cells demonstrated gradual increases in density, number, length, and thickness of stained axons and dendrites from E18 to PND8. In the second experiment, tactile stimulation increased EGR1 induction in OT neurons in the PVN, suggesting oxytocin may be released after social contact in the neonatal nest. These findings demonstrate that early life social experience may induce OT release and alter the developing brain. It is possible that increased OT exposure strengthens the neural circuits underlying bond formation, thus promoting social behavior throughout development.
[Abstract (DOCX)]