| Oxytocin neurophysin 1, encoded by the OXT gene, is a hypothalamic preprohormone that serves as the precursor for the neuropeptide oxytocin and its cognate carrier neurophysin 1, positioning it at the center of neuroendocrine circuits that coordinate parturition, lactation, and social behavior. In magnocellular neurons of the paraventricular and supraoptic nuclei, the OXT neurophysin 1 precursor is proteolytically processed to generate mature oxytocin, which remains associated with neurophysin 1 within neurosecretory vesicles during axonal transport to the posterior pituitary and central terminals, where it is stored until activity dependent calcium dependent exocytosis induces systemic or paracrine release. Once liberated, oxytocin binds its specific G protein–coupled receptor OXTR, which engages both Gαi and Gαq subunits to initiate parallel signaling cascades: Gαq PLC mediated inositol trisphosphate–driven calcium mobilization and protein kinase C activation, together with Gαi dependent inhibition of adenylate cyclase, while downstream mitogen activated protein kinase, CaMK dependent, and phosphoinositide 3 kinase–Akt pathways converge to modulate neuronal excitability, synaptic plasticity, and gene expression. In the periphery, OXTR dependent oxytocin signaling stimulates coordinated uterine smooth muscle contraction during parturition and triggers myoepithelial cell contraction for milk ejection in the mammary gland, whereas in the brain OXTR rich circuits in the amygdala, nucleus accumbens, and prefrontal cortex drive affiliative behavior, social recognition, maternal bonding, and stress related emotional regulation, making oxytocin neurophysin 1 a central node for dissecting social and reproductive neuroendocrinology. Dysregulation of OXT neurophysin 1 expression, vesicular release, or downstream signaling components such as CD38 dependent oxytocin secretion or OXTR linked pathways has been associated with autism spectrum traits, altered social cognition, and mood related phenotypes, and similar perturbations in neuroendocrine oxytocin signaling can contribute to aberrant fluid balance responses or stress axis dysregulation, so that oxytocin neurophysin 1–dependent signaling is ultimately dysregulated in certain neurodevelopmental and neuropsychiatric conditions. |
