Abstract
The oxytocin receptor (OXTR) has been observed in the periphery of neonatal C57BL/6J mice (Mus musculus), including facial regions and the anogenital area. In those studies, ligand specificity was confirmed with a congenital OXTR knockout mouse as well as competitive binding techniques. The aim of this study was to determine if OXTR is present in the same peripheral sites in the neonatal prairie vole (Microtus ochrogaster) for cross-species comparisons. Receptor autoradiography was performed on 20 μm sagittal sections of whole postnatal day 0 (P0) male and female prairie voles using the 125iodinated-ornithine vasotocin ([125I]-OVTA) radioligand. A competition binding assay was used to assess the selectivity of [125I]-OVTA for peripheral OXTR. Radioactive ligand (0.05 nM [125I]-OVTA) was competed against concentrations of 0 and 1000 nM excess unlabeled oxytocin (OXT). Previously identified regions of significant OXTR ligand binding in the mouse were analyzed for comparison: rostral and lateral periodontium, olfactory epithelium, ciliary bodies of the eye, whisker pads, adrenal gland, and anogenital area. We also evaluated the liver and scapular brown adipose tissue, which displayed strong but non-specific signal on film in mice. While there were some areas that showed conserved OXTR ligand binding in the prairie vole (e.g., ciliary body of the eye and the anogenital area), areas showing OXTR ligand binding in the neonatal prairie vole were not identical to OXTR ligand binding in the periphery of the C57BL/6J neonatal mouse. Further, some of the regions measured in the prairie vole suggest sex differences in OXTR ligand binding. Collectively, as is well-established in the central nervous system, these data indicate that patterns of OXTR ligand binding in the infant periphery are species-specific.
Highlights
Oxytocin (OXT) has a well-established role as a neuropeptide known to regulate maternal behavior via central pathways as well as peripheral physiology relating to parturition, the milk let-down reflex and uterine muscle contractions
The goal of the current study was to assess regions previously identified in the mouse for possible oxytocin receptor (OXTR) ligand binding in the neonatal prairie vole (Microtus ochrogaster)
Individual regions of interest were chosen based on our prior report of the distribution of OXTR ligand binding in neonatal mice
Summary
Oxytocin (OXT) has a well-established role as a neuropeptide known to regulate maternal behavior via central pathways as well as peripheral physiology relating to parturition, the milk let-down reflex and uterine muscle contractions. While research has primarily focused on the role of OXT to modulate parental behaviors in adults, less is known about how OXT may shape infant development. The goal of the current study was to assess regions previously identified in the mouse for possible OXTR ligand binding in the neonatal prairie vole (Microtus ochrogaster). Research to date suggests significant differences in OXTR patterns in the brain across different species during development (Vaidyanathan and Hammock, 2016) and in adulthood (Young, 1999), including established differences between the laboratory mouse (Mus musculus) (Hammock and Levitt, 2013) and the prairie vole (Duchemin et al, 2017). The purpose of the current study was to determine if regions found to demonstrate OXTR ligand binding in the neonatal mouse had detectible levels of OXTR in prairie vole neonates
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