Oxytocin signaling in mouse AVPV reveals sexually dimorphic OXTR neurons crucial for maternal behavior

The neuropeptide oxytocin (OXT) plays a critical role in regulating social behaviors, including maternal motivation. While synthesized primarily in the hypothalamus, its diverse central effects are mediated through the oxytocin receptor (OXTR). Current understanding of how oxytocin precisely modulates complex behaviors like maternal care, especially in specific brain regions and in a sex-dependent manner, remains incomplete. This gap highlights the need to identify specific neuronal populations and their mechanisms of action that contribute to the heightened maternal drive observed postpartum, moving beyond broad receptor distribution to circuit-level insights.

This review synthesizes molecular, morphological, and electrophysiological evidence to explore the role of oxytocin signaling within the anteroventral periventricular nucleus (AVPV) of female mice. It integrates findings on OXTR expression patterns, neuronal activity, and interactions with dopaminergic systems, particularly concerning their impact on maternal motivation. The authors discuss how oxytocin and dopamine signaling converge in this region to regulate postpartum behaviors, highlighting previously unrecognized mechanisms by analyzing existing literature and recent discoveries in the field.

A sexually dimorphic population of OXTR-expressing neurons was identified in the AVPV of female mice, with expression being estrogen-dependent and further upregulated during the postpartum period. Functional inactivation of these AVPV-OXTR neurons in dams significantly disrupted specific components of maternal behavior, including pup retrieval and nest building, indicating their essential role. Approximately 30% of these AVPV-OXTR neurons were found to be immunoreactive for tyrosine hydroxylase (TH+), and they also express DOPA decarboxylase, classifying them as dopaminergic. These TH+ AVPV-OXTR neurons exhibit intrinsic pacemaker-like short-burst activity. > OXTR activation was shown to elevate this burst frequency, supporting the idea that these neurons regulate dopaminergic levels in their projection sites and that oxytocin can enhance dopamine output. The close proximity of oxytocin neurons to these OXTR neurons within the AVPV suggests non-conventional release mechanisms, further implicating a novel local interaction between oxytocin and dopamine signaling pathways in regulating maternal motivation.