oxytocine

Oxytocine, also known as oxytocin in many languages, is a peptide hormone and neuropeptide produced in the hypothalamus and released from the posterior pituitary gland. In humans it is encoded by the OXT gene and consists of nine amino acids. It acts on oxytocin receptors (OXTR), G-protein-coupled receptors located in various tissues throughout the body and brain.

Physiological roles include stimulation of uterine contractions during labor and the milk-ejection reflex during breastfeeding. In the brain, oxytocin is associated with social bonding, maternal behaviors, and aspects of social cognition and trust. Its effects are context-dependent and can be influenced by hormonal state, environmental cues, and individual differences.

Regulation of release involves neural signals from the hypothalamus in response to cervical and uterine stretching, nipple stimulation, and certain stressors. Estrogen can upregulate oxytocin synthesis and receptor expression. Peripheral actions (in the uterus and mammary glands) and central actions (in the brain) may be partially separable due to differences in how the molecule accesses central targets.

Clinical use and pharmacology: Synthetic oxytocin is used to induce or augment labor and to reduce postpartum hemorrhage. Commercial preparations include Pitocin and Syntocinon. Potential adverse effects include uterine tachysystole, fetal distress, and hyponatremia from fluid imbalance. Oxytocin has a short circulatory half-life and limited direct penetration of the blood-brain barrier, so central effects are thought to arise from signaling pathways outside the blood–brain barrier or from local release within the brain.