Flexible adjustment of oxytocin neuron activity in mouse dams revealed by microendoscopy

Oxytocin (OT) neurons in the hypothalamic paraventricular nucleus (PVH) play an important role in various physiological and behavioral processes, including the initiation of milk ejection and the regulation of maternal behaviors. However, their activity patterns at the single-cell level remain poorly understood. Using microendoscopic Ca²⁺ imaging in freely moving mouse dams, we demonstrate highly correlated pulsatile activity among individual OT neurons during lactation. The number of OT neurons engaged in the pulsatile activity significantly increased, along with a broadening of individual waveforms in the mid-lactation stage. Notably, only ~10% of the imaged OT neurons exhibited a significantly elevated response during pup retrieval, a hallmark of maternal behaviors, with a magnitude smaller than that observed during lactation. Collectively, these findings demonstrate the utility of microendoscopic imaging for PVH OT neurons and highlight the flexible adjustments of their individual activity patterns in freely behaving mouse dams.