Para-uterine imaging protocol: Stabilizing living mouse embryos within the maternal abdomen for in vivo imaging and visually guided physiology

In vivo imaging is critical for interrogating brain circuits but is limited before birth. Here, we describe a protocol for para-uterine stabilization of living mouse embryos, enabling recordings from individual neurons and neuronal processes. We describe steps to extract embryos from the amniotic sac, place them into externally stabilized holders, expose their brains, and then transfer them for imaging, all while keeping the umbilical cords intact. Through this method, para-uterine imaging enables tools from adult head-fixed mice to generalize to embryos. For complete details on the use and execution of this protocol, please refer to Munz et al.¹.