Two kinds of melatonin receptors, MT l and MT2exist on the membrane and cytoplasma of brain cells. These indicatethat the human embryo brain is a target organ of melatonin. It can acton the brain directly and regulate the brain function.

• 人胚胎脑组织细胞存在 MT1、MT2 两种褪黑素受体，位干细胞膜、细胞浆内，证明脑组织是褪黑素作用的靶器官，褪黑素可能直接作用于脑组织，调节胚胎脑组织的功能及发育。