Oxytocin and social neuroscience - sexually dimorphic OXTR neurons in mouse preoptic area

Oxytocin is synthesized primarily by neurons in the hypothalamus, and it exerts diverse central and peripheral effects through activation of its receptor, the oxytocin receptor (OXTR). A sexually dimorphic population of OXTR-expressing neurons was identified in the anteroventral periventricular nucleus (AVPV) in the preoptic area of female mice. The expression of OXTR in the AVPV is estrogen-dependent and becomes further upregulated during the postpartum period. Functional inactivation of these neurons in dams disrupts specific components of maternal behavior, including pup retrieval and nest building, indicating that their activity is essential for normal maternal behavior. Furthermore, approximately 30% of these AVPV-OXTR neurons are immunoreactive to tyrosine hydroxylase (TH⁺). Because these neurons also express DOPA decarboxylase, the enzyme that converts L-DOPA to dopamine, they are considered dopaminergic. TH⁺ AVPV-OXTR neurons generate intrinsic pacemaker-like short-burst activity, and OXTR activation elevates burst frequency, supporting the idea that these neurons regulate dopaminergic levels in their projection sites and that oxytocin can enhance dopamine output. Moreover, oxytocin neurons are near these OXTR neurons within the AVPV-so close that conventional axonal release is unlikely to account for their interaction. Given that both dopamine and oxytocin signaling in the preoptic area are required for the heightened maternal motivation observed during the postpartum period, the presence of both oxytocin and OXTR-expressing neurons in the AVPV points to previously unrecognized mechanisms contributing to this enhancement. This review discusses the potential role of oxytocin signaling in the AVPV in the regulation of maternal motivation, integrating molecular, morphological, and electrophysiological evidence.