Lasting consequences on physiology and social behavior following cesarean delivery in prairie voles.

Cesarean delivery is associated with diminished plasma levels of several 'birth-signaling' hormones, such as oxytocin and vasopressin. These same hormones have been previously shown to exert organizational effects when acting in early life. For example, our previous work found a broadly gregarious phenotype in prairie voles exposed to oxytocin at birth. Meanwhile, cesarean delivery has been previously associated with changes in social behavior and metabolic processes related to oxytocin and vasopressin. In the present study, we investigated the long-term neurodevelopmental consequences of cesarean delivery in prairie voles. After cross-fostering, vole pups delivered either via cesarean or vaginal delivery were studied throughout development. Cesarean-delivered pups responded to isolation differently in terms of their vocalizations (albeit in opposite directions in the two experiments), huddled in less cohesive groups under warmed conditions, and shed less heat. As young adults, we observed no differences in anxiety-like or alloparental behavior. However, in adulthood, cesarean-delivered voles of both sexes failed to form partner preferences with opposite sex conspecifics. In a follow-up study, we replicated this deficit in partner-preference formation among cesarean-delivered voles and were able to normalize pair-bonding behavior by treating cesarean-delivered vole pups with oxytocin (0.25 mg/kg) at delivery. Finally, we detected minor differences in regional oxytocin receptor expression within the brains of cesarean-delivered voles, as well as microbial composition of the gut. Gene expression changes in the gut epithelium indicated that cesarean-delivered male voles have altered gut development. These results speak to the possibility of unintended developmental consequences of cesarean delivery, which currently accounts for 32.9 % of deliveries in the U.S. and suggest that further research should be directed at whether hormone replacement at delivery influences behavioral outcomes in later life.