Plasticity of neuro-endocrine cells induced by sex hormone.

已知雄性动物下丘脑中的催产素神经元是由催产素引起的。最近，我们已经证明，处女和怀孕大鼠的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性反应，并在分娩后恢复到抑制反应。这可能是一种新型的神经可塑性。本研究旨在探讨逆转OXT神经元对OXT反应的关键因素及雌雄大鼠OXT反应的膜机制的差异。1.应用OXT兴奋去卵巢处女大鼠视上OXT神经元。说明处女大鼠的抑制反应可能来源于卵巢激素。2.在去卵巢的雌性大鼠中，OXT抑制了OXT神经元的活动，提示卵巢激素中的雌激素是一种候选的逆转因子。3.在三苯氧胺预处理的处女大鼠中，OXT诱导OXT神经元的兴奋性反应。证实雌激素是逆转下丘脑OXT神经元对OXT反应的关键因素。4.同样的OXT受体拮抗剂能有效地阻断雄性和去卵巢处女大鼠的兴奋性反应，以及正常和雌激素处理的处女大鼠对OXT的抑制反应。5.雄性大鼠OXT神经元的兴奋反应导致Na~+通道开放，而处女大鼠的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受体的改变，而是由于功能性离子通道的重新分布。

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.