Proposed mechanism of action of oxytocin (OT). This hormone induces contraction of the myoepithelial cells (green arrow), via a G protein receptor. OT also induces exocytosis of milk in MEC (blue arrow) by intracellular Ca2+ increased pathways. Myoepithelial cells contraction and MEC exocytosis induce milk ejection; the continued milk ejection results in a decrease of a protein milk synthesis reversible blocker: feedback inhibitor of lactation (FIL), and this milk and FIL removal of mammary gland will promote then the milk synthesis.
