Developmental trajectories and influences of environmental complexity on oxytocin receptor and vasopressin 1A receptor expression in male and female prairie voles.

Nonapeptide receptors, like oxytocin receptor (OTR) and vasopressin 1a receptor (V1aR), modulate a variety of functions across taxa, and mediate phenotypic variation within and between species. Despite the popularity of studying nonapeptides in adults, developmental perspectives on properties of OTR and V1aR expression are lacking. Study of prairie voles (Microtus ochrogaster) has facilitated an understanding of mechanisms of social behavior and provides great potential to inform how early life experiences alter phenotype. We provide the first comprehensive profiling of OTR and V1aR in male and female prairie voles across postnatal development and into adulthood. Differences in receptor densities across the forebrain were region- and sex-specific. Postnatal changes in receptor expression fell into four themes: (a) constant over time, (b) increasing with age, (c) decreasing with age, or (d) peaking during late pre-weaning (postnatal day 15-21). We also examined the influence of post-weaning social and spatial enrichment (i.e., environmental complexity) on OTR and V1aR. Environmental complexity appeared to promote expression of OTR in males and females, and reduced expression of V1aR across several brain regions in males. Our results show that nonapeptide receptor profiles are plastic over development and suggest that different patterns of expression might represent functional differences in sensitivity to nonapeptide activation over a period when social environments are dynamic. Our results on environmental complexity suggest that nonapeptide sensitivity responds flexibly to different environmental contexts during development. Understanding the developmental trajectories of nonapeptide receptors provides a better understanding of the dynamic nature of social behavior and the underlying mechanisms.