Oxytocin exerts its effects by binding to oxytocin receptors (OXTR), which are G‑protein coupled receptors widely expressed in both central and peripheral tissues[6]. In the brain, oxytocin acts as a neuromodulator: it is produced in the hypothalamus and released from the posterior pituitary, and also directly released within brain regions involved in emotion and social behavior. Activation of central OXTR influences neurotransmitter systems (e.g., enhancing prosocial signaling via dopamine and reducing stress responses via the hypothalamic–pituitary–adrenal axis)[7]. These actions underlie oxytocin’s observed effects on increasing trust, empathy, and social bonding. Peripherally, oxytocin causes contraction of smooth muscles—for example, uterine muscle contraction during labor and milk ejection in lactation[1]. It also can modulate pain perception and inflammation; studies show subcutaneous oxytocin produces local analgesia, likely by acting on sensory nerves or immune cells in skin tissue[8]. Importantly, oxytocin does not significantly cross the blood–brain barrier from the bloodstream. Thus, peripheral administration primarily targets peripheral OXTR (with some indirect central effects), while intranasal administration is thought to better engage central receptors by bypassing the blood–brain barrier. Overall, oxytocin’s mechanism in research contexts involves enhancing social‑affiliative behaviors and modulating physiological stress and metabolic processes through its receptor‑mediated signaling pathways.
