Plasticity of neuro-endocrine cells induced by sex hormone.

已知雄性动物下丘脑的催产素（OXT）神经元是由OXT引起的。最近，我们已经证明，在未交配和怀孕的大鼠中，OXT神经元对OXT的抑制反应在分娩和哺乳动物中逆转为兴奋反应，并在分娩后恢复为抑制反应。这可能是一种新型的神经可塑性。本研究旨在探讨氧化应激神经元对氧化应激反应逆转的关键因素，以及雌雄大鼠氧化应激反应的膜机制差异。经卵巢切除的雌性大鼠视上OXT神经元被OXT激活。这说明雌性大鼠的抑制反应可能来源于卵巢激素。在雌性雌激素处理的去势雌性大鼠中，OXT神经元活性被OXT抑制。提示卵巢激素之一的雌激素是逆转因子的候选因子。在用他莫昔芬和抗雌激素预处理的雌性大鼠中，OXT诱导了OXT神经元的兴奋反应。雌激素是下丘脑OXT神经元对OXT反应逆转的关键因素。同种OXT受体拮抗剂可有效阻断雄性和去卵巢雌性大鼠对OXT的兴奋反应，以及正常和雌激素处理的雌性大鼠对OXT的抑制反应。可能对OXT的兴奋性和抑制性反应都是由同一类型的OXT受体介导的。雄性大鼠OXT神经元的兴奋性反应导致Na^+通道的打开，而雌性大鼠的Na^+通道不参与抑制反应。这些结果表明，雌激素逆转OXT神经元的OXT反应不是由于OXT受体的修饰，而是由于功能性离子通道的重新分配。

It has been known that oxytocin (OXT) neurons in the hypothalamus were by OXT in male animals. Recently, we have demonstrated that inhibitory responses of OXT neurons to OXT in virgin and pregnant rats reverse to excitatory responses in delivering and lactating animals and return to inhibitory responses after delivery. It may be a new type of neural plasticity. The present work was carried out to investigate the key factor for reverse the response in OXT neurons to OXT and the difference of membrane mechanisms of responses to OXT between male and female rats.1.Supraoptic OXT neurons of ovariectomized virgin female rat were excited by OXT application. It means the inhibitory responses in virgin female rats may be derived from ovarian hormones.2.In Ovariectimized virgin female rat treated with estrogen, activity of OXT neurons was inhibited by OXT.It indicates estrogen, one of ovarian hormone, is a candidate of reversal factor.3.In virgin female rats pretreated with tamoxifen, anti-estrogen, OXT induced excitatory responses in OXT neurons. It is confirmed that estrogen is the key factor for reverse the response in the hypothalamic OXT neurons to OXT.4.Both excitatory responses in male and ovariectomized virgin female rats and inhibitory responses in normal and estrogen treated virgin female rats to OXT were effectively blocked by same OXT receptor antagonist. It is possible that both excitatory and inhibitory responses to OXT are mediated same type of OXT receptor.5.Excitatory response of OXT neurons in male rats results in opening of Na^+ channel but the channel did not participate in inhibitory response in virgin femaleThese results suggest that estrogen reversal of OXT response in OXT neurons is not due to modification at OXT receptor but due to redistribution of the functioning ionic channels.