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目的： 观察模拟失重大鼠在硝普钠诱发瞬间低血压后延髓内脏带儿茶酚胺能神经元的Ｆｏｓ表达． 方法： 用尾部悬吊大鼠４ ｗ ｋ 模拟失重，静脉注射硝普钠制作低血压模型，用抗Ｆｏｓ蛋白和抗酪氨酸羟化酶（ＴＨ）的双重免疫组织化学方法（ＡＢＣ法），观察延髓内脏带内Ｆｏｓ 蛋白表达及其与ＴＨ阳性神经元的共存． 结果： 在低血压处理后，有相当数量的Ｆｏｓ阳性细胞出现在延髓内，它们主要局限在延髓内脏带内，并以孤束核与延髓腹外侧区较为密集． 但与单纯模拟失重和单纯给药大鼠比较，Ｆｏｓ阳性细胞数和腹外侧区Ｆｏｓ／ＴＨ 双标细胞占ＴＨ阳性细胞的比例明显减少，且ＴＨ神经元免疫反应减弱． 结论： 延髓内脏带内对瞬间血压下降起反应神经元（Ｆｏｓ阳性细胞）数量的下降以及儿茶酚胺能神经元表达Ｆｏｓ的降低，可能与模拟失重大鼠交感系统功能的减弱有关．
Objective: To observe the Fos expression of catecholaminergic neurons in the medullary visceral zone of simulated weightless rats after sodium nitroprusside induced transient hypotension. Methods: Hypotension model was made by intravenous injection of sodium nitroprusside after 4 wk simulated weightlessness in tail-suspended rats. The anti-Fos protein and anti-tyrosine hydroxylase (TH) double immunohistochemical method (ABC method) To observe the expression of Fos protein in medullary visceral zone and its co-existence with TH-positive neurons. Results: After Hypotension, a considerable number of Fos positive cells appeared in the medulla. They were mainly confined to the medullary visceral zone and were more densely located in the solitary nucleus and medulla oblongata. However, the numbers of Fos positive cells and Fos / TH double-labeled cells in the ventrolateral region were significantly decreased compared with those in the purely simulated weightless rats and the rats administered with melatonin alone, and TH neuronal immune response was weakened. CONCLUSION: The decrease of the number of reactive neurons (Fos positive cells) and the decrease of Fos expression in cortical neurons in medulla oblongata visceral zone may be related to the decrease of sympathetic system function in rats with simulated weightlessness.