模拟失重大鼠延髓 FOS蛋白表达及脊髓侧角神经元直径的变化

FOS EXPRESSION IN THE NEURONS OF MEDULLA OBLONGATA AND CHANGES OF NEURON SIZE IN THE INTERMEDIOLATERAL NUCLEUS OF THE SPINAL CORD DURING SIMULATED WEIGHTLESSNESS

为观察模拟失重大鼠延髓 FOS表达以及脊髓交感节前神经元是否发生一定改变 ,本研究采用尾部悬吊大鼠模型模拟失重影响 ,用抗 FOS蛋白和抗酪氨酸羟化酶 ( TH)双重免疫组织化学反应和 Nissl染色法 ,观察了 4周的在模拟失重下延髓 FOS蛋白表达与 TH阳性神经元的关系以及脊髓 C8、T1侧角细胞大小的改变 ,并与对照大鼠进行比较。结果显示 :与对照组大鼠比较 ,模拟失重大鼠出现了以下的改变 :( 1) FOS蛋白表达主要局限在延髓内脏带 ( MVZ)区 ,并以背内侧的孤束核与腹外侧区较为密集 ,并且发现有近 3 0 %的 TH神经元出现 FOS表达 ;( 2 )三叉神经脊束核尾侧亚核和薄束核亦出现 FOS表达 ;( 3 ) C8、T1侧角细胞胞体增大。本研究提示 ,在 4周模拟失重条件下 MVZ可能参与失重状态下心血管适应性变化的中枢调控 ,且儿茶酚胺能神经元参与这种作用的调节 ;脊髓侧角细胞发生代偿性增大变化。

The aim of this study was to observe whether Fos protein was expressed in medulla oblongata and the size of the sympathetic preganglionic neurons in the rat cervical spinal cord was changed during simulated weightlessness. The tail suspension rat model was used to simulate the cardiovascular deconditioning of weightlessness. FOS and/or tyrosine hydroxylase (TH) positive neurons in medulla oblongata were revealed by a double immunohistochemical staining method. The neurons in the intermediolateral nucleus of the spinal cord (C8～T1) were stained by Nissl staining method. The results were compared with that of the synchronous control rats. Four weeks after simulated weightless, we observed the following changes: (1) FOS positive neurons were mainly localized in the medullary visceral zone, especially in the dorsomedial subnucleus of the nucleus tractus solitariis and ventrolateral medulla, and approximately 30% of the TH positive neurons expressed FOS like immunoreactivity; (2) FOS positive neurons were also found in the caudal spinal trigeminal nucleus and gracile nucleus; (3) the size of the neurons in the intermediolateral nucleus of the C8～T1 cord segments were enlarged. It is suggested that besides the peripheral cardiovascular effector mechanisms elucidated in our previous works, central integration of cardiovascular control mechanisms might also be involved in the genesis of postflight cardiovascular dysfunction and orthostatic intolerance in astronauts. (Figures 1～6 on plate 9)