Freund-Mercier M J, Stoeckel M E
Laboratoire de Physiologie générale, URA CNRS, Strasbourg, France.
Adv Exp Med Biol. 1995;395:185-94.
Oxytocin (OT) is known to exert a facilitatory effect on its own pulsatile release during the milk ejection reflex. Several experimental approaches strongly suggested that this effect occurred in the supraoptic and paraventricular magnocellular hypothalamic nuclei where the OT neurones are concentrated. In these nuclei autoradiographic techniques failed however to detect OT receptors. In the presently reported data, OT binding sites were visualized in the supraoptic, paraventricular and accessory magnocellular nuclei in lactating rats, suckled or not, after acute intracerebroventricular injection of an OT antagonist. No such labelling occurred either in untreated lactating rats or in OT antagonist treated male rats. The combined application of histoautoradiographic and immunocytochemical techniques revealed that the OT binding sites were concentrated on magnocellular OT cell bodies and dendrites but not on their axons and endings in the pituitary neural lobe. The presently detected somatodendritic autoreceptors on OT neurones probably mediate the facilitatory effect of OT on its own release during the milk ejection reflex.
已知催产素（OT）在排乳反射期间对其自身的脉冲式释放具有促进作用。多种实验方法有力地表明，这种作用发生在视上核和室旁核的下丘脑大细胞中，OT神经元集中于此。然而，在这些核中，放射自显影技术未能检测到OT受体。在目前报告的数据中，急性脑室内注射OT拮抗剂后，无论是否哺乳，在泌乳大鼠的视上核、室旁核和附属大细胞核中均可见OT结合位点。在未处理的泌乳大鼠或经OT拮抗剂处理的雄性大鼠中均未出现此类标记。组织放射自显影和免疫细胞化学技术的联合应用表明，OT结合位点集中在大细胞OT细胞体和树突上，而不在垂体神经叶中的轴突和末梢上。目前在OT神经元上检测到的树突体自身受体可能介导了OT在排乳反射期间对其自身释放的促进作用。
