Honda Kazumasa
Department of Physiology, Fukui Medical University, Japan.
J Reprod Dev. 2003 Feb;49(1):1-11. doi: 10.1262/jrd.49.1.
To explore mechanisms of osmotic control of neurohypophysial hormone release, electrical activity of magnocellular neurons (MCNs) in the hypothalamus, related neurons and efferent renal sympathetic nerve activity (RSNA) were recorded from urethane-anesthetized rats. Local osmotic stimulation applied to organum vasculosum of the lamina terminalis (OVLT) or median preoptic nucleus (MnPO) excited MCNs. Although OVLT neurons projected to MCNs were unresponsive to hyperosmotic stimulation, those projected to MnPO and also receiving excitatory inputs from MCNs, were excited by it. MnPO neurons, which were driven by OVLT stimulation and projected to MCNs, were also osmosensitive. Excitatory connections thus exist from MCNs to OVLT, from OVLT to MnPO and from MnPO to MCNs. Neurons in each of these connections were osmosensitive. This circuit thus appears to constitute an osmoreceptor complex essential for the osmoreception of MCNs. MnPO neurons constituting a part of the osmosensitive circuit were also sensitive to hemodynamic change. Thus this circuit may integrate hemodynamic and osmotic information. Local anesthesia of MnPO diminished activation of RSNA and pressor response induced by third cerebroventricular injection of hypertonic saline. The results suggest that the osmosensitive circuit is involved in body fluid regulation not only by controlling vasopressin secretion but also by modulating sympathetic outflow.
为探究神经垂体激素释放的渗透调节机制，从经乌拉坦麻醉的大鼠记录下丘脑大细胞神经元（MCNs）、相关神经元的电活动以及肾交感神经传出活动（RSNA）。对终板血管器（OVLT）或视前正中核（MnPO）进行局部渗透刺激可兴奋MCNs。虽然投射至MCNs的OVLT神经元对高渗刺激无反应，但那些投射至MnPO且还接受MCNs兴奋性输入的神经元会被高渗刺激所兴奋。由OVLT刺激驱动并投射至MCNs的MnPO神经元也对渗透压敏感。因此，存在从MCNs到OVLT、从OVLT到MnPO以及从MnPO到MCNs的兴奋性连接。这些连接中的每一个连接的神经元都对渗透压敏感。因此，该回路似乎构成了MCNs渗透压感受所必需的渗透压感受器复合体。构成渗透压敏感回路一部分的MnPO神经元也对血流动力学变化敏感。因此，该回路可能整合血流动力学和渗透压信息。MnPO局部麻醉可减弱第三脑室注射高渗盐水所诱导的RSNA激活和升压反应。结果表明，渗透压敏感回路不仅通过控制血管加压素分泌，还通过调节交感神经输出参与体液调节。
