Oxytocin

Synthesized hormones in the hypothalamus, in the paraventricular nuclei, then transported with axonal flow to the nerve endings of the adenohypophysis. From there, after appropriate stimulation, they enter the bloodstream, overcoming the blood-brain barrier. Oxytocin is a cyclic nanopeptide, with cysteine in positions 1 and 6:

Its action is dependent on the N-terminal cysteine amino group, tyrosine phenolic group, asparagine and glycine amide groups, and disulfide bond. Oxytocin is synthesized in the form of preprooxytocin. In the blood, it is free and inactivated in the liver. Oxytocin targets are mammary glands and uterine smooth muscles. It acts through Ca²⁺ and phosphatidylinositol metabolites. Oxytocin promotes contraction of mammary gland myoepithelial cells, facilitating milk transport into the alveolar duct system and its secretion. The name oxytocin is related to the stimulation of childbirth by enhancing uterine muscle contractions. Its physiological importance lies in promoting milk secretion.

Source | Glossary of Most Commonly Used Biomedical Terms and Concepts | Lithuanian University of Health Sciences | Academician Professor Antanas Praškevičius, Professor Laima Ivanovienė