EN
Oxytocin is a neuropeptide with functions including the development and expression of social behavior. Despite its significance, brain-wide spatial and temporal expression patterns of the oxytocin receptor (OTR), the main mediator of the oxytocin ligand, remain largelyunknown. Here, we examined the expression patterns of oxytocin receptor-positive neurons at different developmental time points (P7, P14, P21, P28) and in adulthood (P56) using a transgenic reporter line (OTR‑GFP). We used serial two-photon tomography for whole brain imaging at cellular resolution and a data processing pipeline that allows us to map fluorescently labeled cells throughout the entire brain with our newly developed postnatal 3D atlases. We found temporally different expression peaks in different brain regions including neocortex. We further investigated OTR expression patterns in OTR heterozygote reporter mice (OTR-Venus) and found an overall delayed expression pattern, which may be linked to impaired social behavior in the OTR‑Venus mice. We envision that our highly detailed OTR expression map will guide future circuit-based investigations to understand the mechanisms of oxytocin signaling in various behavioral assays.