Wang H, Ward A R, Morris J F
Department of Human Anatomy, University of Oxford, UK.
Neuroscience. 1995 Oct;68(4):1179-88. doi: 10.1016/0306-4522(95)00186-m.
Oestrogen has many direct or indirect actions upon the magnocellular system of the hypothalamus. We have examined the possibility of acute actions of oestrogen upon the magnocellular system by stimulating slices of supraoptic nucleus in vitro with various concentrations of oestrogen, for varying lengths of time, and assessing the intrahypothalamic release of oxytocin and vasopressin under these conditions. Slices were stimulated in the presence of tannic acid, which precipitates extracellular protein and thereby stabilizes exocytosed neurosecretory granule cores. Stimulation for 5 or 20 min of slices of hypothalamus containing the supraoptic nuclei with 2.66 nM-26.6 microM 17 beta-oestradiol benzoate caused the exocytosis of granules from both dendrites and cell bodies of the magnocellular neurons; exocytosis from the dendrites predominated. Granules of both oxytocin- and vasopressin-producing cells were exocytosed to a similar extent. The incidence of exocytosis of both hormones after stimulation by oestrogen was significantly higher than after exposure either to physiological saline or to 17 alpha-oestradiol, but significantly lower than after stimulation by 56 mM potassium. The various doses of steroid and durations of stimulation all resulted in similar amounts of captured exocytosis. Furthermore, the oestradiol-induced release was not inhibited by removal of extracellular calcium, whereas the potassium-stimulated release was abolished. Exposure for 20 min to either testosterone or progesterone did not induce intranuclear release of significant numbers of neurosecretory granules from the magnocellular neurons. In contrast to its effect on the hypothalamus, 26.6 microM oestradiol for either 20 min or 5 min did not induce exocytosis of neurosecretory granules from the posterior pituitary. We conclude that oestrogen can exert acute non-genomic actions on the magnocellular neurons to promote intrahypothalamic release of oxytocin and vasopressin. This effect is probably direct on the magnocellular neurons as it is not dependent on external calcium. Such actions may be important in the development of the functional and morphological plasticity of the magnocellular system that occurs in parturition and lactation.
雌激素对下丘脑的大细胞系统有许多直接或间接作用。我们通过在体外以不同浓度的雌激素刺激视上核切片、刺激不同时长，并评估在此条件下下丘脑内催产素和血管加压素的释放，研究了雌激素对大细胞系统的急性作用的可能性。切片在鞣酸存在的情况下受到刺激，鞣酸可沉淀细胞外蛋白质，从而稳定胞吐的神经分泌颗粒核心。用2.66 nM - 26.6 μM苯甲酸雌二醇刺激含有视上核的下丘脑切片5或20分钟，会导致大细胞神经元的树突和细胞体中的颗粒发生胞吐作用；树突的胞吐作用占主导。催产素和血管加压素产生细胞的颗粒胞吐程度相似。雌激素刺激后两种激素的胞吐发生率显著高于暴露于生理盐水或17α - 雌二醇后的发生率，但显著低于56 mM钾刺激后的发生率。不同剂量的类固醇和刺激时长均导致类似数量的捕获胞吐。此外，雌二醇诱导的释放不受细胞外钙去除的抑制，而钾刺激的释放则被消除。暴露于睾酮或孕酮20分钟均未诱导大细胞神经元大量神经分泌颗粒的核内释放。与对下丘脑的作用相反，26.6 μM雌二醇处理20分钟或5分钟均未诱导神经垂体神经分泌颗粒的胞吐作用。我们得出结论，雌激素可对大细胞神经元发挥急性非基因组作用，以促进下丘脑内催产素和血管加压素的释放。这种作用可能直接作用于大细胞神经元，因为它不依赖于细胞外钙。此类作用可能在分娩和哺乳过程中发生的大细胞系统功能和形态可塑性的发展中起重要作用。
