Fagette S, Fareh J, Cottet-Emard J M, Pequignot J M, Gauquelin G, Gharib C
Lab. Physiologie de l'Environnement, Lyon, France.
Life Sci. 1993;53(7):555-61. doi: 10.1016/0024-3205(93)90712-c.
The loss of appropriate cardiovascular reflexes which contributes to the cardiovascular deconditioning observed after an exposure to actual or simulated microgravity (in man or animals) is well known, but the mechanisms responsible remain unclear. This protocol, a 2.5 h hindlimb suspension in rats, was undertaken to study the early adaptation of the sympathetic neurons involved in arterial pressure regulation: we determined central norepinephrine (NE) turnover in the brainstem catecholaminergic cell groups responsible for the central cardiovascular regulation i.e. A1, A2 (rostral and caudal), A5 and A6 cell groups and peripheral NE turnover in target organs (heart and kidneys). The NE turnover in suspended rats significantly decreased in rostral A2 (48% p < 0.001), caudal A2 (52% p < 0.001) and A5 (40% p < 0.05) cell groups while it was unchanged in A1 and A6 cell groups compared with rats attached to the suspension device but maintained in the horizontal position. The short term hindlimb suspension did not alter the NE turnover in cardiac atria and ventricles or in kidneys nor did it alter the blood variables studied (hematocrit, osmolality, plasma sodium, potassium, proteins and renin concentration). We concluded that a 2.5 h hindlimb suspension reduced noradrenergic neuron activity in A2 and A5 cell groups involved in the central control of arterial pressure and particularly in the baroreceptor reflex mechanisms. This duration was probably not sufficient to modify the NE turnover in the two peripheral organs studied.
在暴露于实际或模拟微重力环境后（在人类或动物中）所观察到的心血管去适应现象，其部分原因是适当的心血管反射丧失，这一点已为人熟知，但相关机制仍不清楚。本实验采用对大鼠后肢进行2.5小时悬吊的方法，来研究参与动脉血压调节的交感神经元的早期适应性变化：我们测定了负责中枢心血管调节的脑干儿茶酚胺能细胞群（即A1、A2（头端和尾端）、A5和A6细胞群）中的中枢去甲肾上腺素（NE）周转率，以及靶器官（心脏和肾脏）中的外周NE周转率。与附着于悬吊装置但保持水平位置的大鼠相比，悬吊大鼠的头端A2细胞群（降低48%，p<0.001）、尾端A2细胞群（降低52%，p<0.001）和A5细胞群（降低40%，p<0.05）中的NE周转率显著降低，而A1和A6细胞群中的NE周转率未发生变化。短期后肢悬吊并未改变心脏心房和心室或肾脏中的NE周转率，也未改变所研究的血液变量（血细胞比容、渗透压、血浆钠、钾、蛋白质和肾素浓度）。我们得出结论，2.5小时的后肢悬吊降低了参与动脉血压中枢控制、特别是压力感受器反射机制的A2和A5细胞群中去甲肾上腺素能神经元的活性。该时长可能不足以改变所研究的两个外周器官中的NE周转率。
