Central Regulation of Autonomic Nervous System and Endocrine System during Circulatory Shock

在循环系统休克的早期阶段，交感神经反射和荷尔蒙因素被认为可以补偿以防止循环恶化。然而，调节和协调这种反应的中枢神经系统(CNS)机制在很大程度上是未知的。本研究旨在确定脑内参与循环休克时心血管系统中枢调节的物质(S)。采用推拉灌流的方法，研究了清醒大鼠出血后第四脑室释放的促甲状腺激素释放激素(TRH)的变化。已知中央给药的TRH具有独立于其脑垂体活动的心血管效应。在本研究中，我们发现：1)对照组大鼠灌流液中TRH浓度在140分钟内保持恒定。2)在回输30%的估测总血后，在灌流的前20分钟内显著升高，并很快恢复到初始水平。3)脑室注射正常兔血清和TRH抗血清3小时后，对血压和心率均无明显影响。4)出血后，注射TRH抗血清的动物血压下降幅度明显大于注射正常兔血清的动物，且持续时间更长。后一组动物出血后即刻出现的心动过速趋势被抑制，但未见明显变化。提示脑内TRH参与清醒大鼠出血后心血管系统的中枢调节。然而，在正常状态下，它对中枢心血管调节没有任何显著作用。

In the early stage of circulatory shock, sympathetic reflexes and hormonal factors are known to compensate to prevent deterioration of the circulation. However, the central nervous system(CNS) mechanisms that mediate and coordinate such responses are largely unknown. This study is designed to identify the substance(s) in the brain, which are involved in central regulation of cardiovascular system during circulatory shock. I have studied the changes of brain thyrotropin-releasing hormone(TRH), as one of the candidates of such substances, released in the fourth ventricle of conscious rat after bleeding using a push-pull perfusion method. Centrally administered TRH is known to have the cardiovascular effect independent of its pituitary actions. In this study,it has been revealed that; 1) The concentration of TRH in the perfusate remained constant during the 140 min perfusion period in the control rat. 2) It was significantly increased during the first 20 min of perfusion immediately after withdrawing of 30% of the estimated total blood and it soon returned to the initial level. 3) Administration of neither normal rabbit serum nor antiserum of TRH into the ventricle had any significant effects on blood pressure or heart rate for 3 hr in the control animal. 4) After bleeding, animals that received TRH-antiserum showed a significantly greater decrease in blood pressure and longer duration of this decreased level than animals that received normal rabbit serum. The tendency of tachycardia which was seen immediately after bleeding in the latter animals was suppressed in the former animals, but no significant changes were detected. These results suggest that endogenous brain TRH is involved in the central regulation of the cardiovascular system after bleeding in conscious rats. However, it does not have any significant role in the central cardiovascular regulation in the normal state.