Flexible Adjustment of Oxytocin Neuron Activity in Mother Mice Revealed by Microendoscopy

Oxytocin (OT) neurons in the hypothalamic paraventricular nucleus (PVH) play an important role in a range of physiological and behavioral processes, including the initiation of milk ejection and the regulation of parental behaviors in mothers. However, their activity patterns at the single-cell level remain poorly understood. Using microendoscopic Ca ²⁺ imaging in freely moving mother mice, we demonstrate highly correlated pulsatile activity among individual OT neurons during lactation. The number of OT neurons engaged in the pulsatile activity, along with the characteristics of individual waveforms, was dynamically modulated by lactation and weaning experiences. Notably, only ∼10% of the imaged OT neurons exhibited a significantly elevated response during pup retrieval, a hallmark of maternal behaviors, with a magnitude 18 times 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 mother mice.