Sawano F, Shibamoto T, Hayashi T, Saeki Y
Department of Physiology, Shinshu University School of Medicine, Nagano, Japan.
Am J Physiol. 1995 Apr;268(4 Pt 2):R859-64. doi: 10.1152/ajpregu.1995.268.4.R859.
We determined effects of vena caval occlusion-induced systemic hypotension of 50 mmHg lasting 10 min (VCO) on efferent sympathetic nerve activity (SNA) and sympathetic baroreflex responsiveness. We recorded simultaneously SNA to the kidney (RNA), heart (CNA), spleen (SpNA), and liver (HNA) in anesthetized dogs. Baroreflex sensitivity was assessed using the ratio of a reflex SNA increase to a mean arterial pressure fall, which was also induced by caval occlusion. During VCO, SNA initially and equivocally increased, followed by recovery toward baseline. Cervical vagotomy attenuated the VCO-induced initial sympathoexcitation and subsequently maintained SNA at higher levels than those of intact animals, a finding basically similar to hemorrhagic hypotension [S. Koyama, F. Sawano, Y. Matsuda, Y. Saeki, T. Shibamoto, T. Hayashi, Jr., Y. Matsubayashi, and M. Kawamoto. Am. J. Physiol. 262 (Regulatory Integrative Comp. Physiol. 31): R579-R585, 1992]. At 5 min after releasing VCO, the baroreflex responsiveness was significantly attenuated: RNA, 79 +/- 11%; CNA, 78 +/- 8%; HNA, 60 +/- 16%; SpNA, 81 +/- 13% of the corresponding baseline. Fifteen minutes after VCO, this attenuation disappeared. Either vagotomy or pretreatment with intravenous vasopressin V1 receptor antagonist abolished this baroreflex attenuation. In conclusion, systemic hypotension to 50 mmHg for 10 min causes transient attenuation of sympathetic baroreflex sensitivity due to circulating vasopressin released by unloading of cardiopulmonary receptors during hypotension.
我们测定了腔静脉闭塞诱导的持续10分钟的50 mmHg全身性低血压（VCO）对传出交感神经活动（SNA）和交感压力反射反应性的影响。我们在麻醉犬中同时记录了肾（RNA）、心脏（CNA）、脾脏（SpNA）和肝脏（HNA）的SNA。使用反射性SNA增加与平均动脉压下降的比值评估压力反射敏感性，平均动脉压下降也是由腔静脉闭塞诱导的。在VCO期间，SNA最初有不明确的增加，随后恢复至基线水平。颈迷走神经切断术减弱了VCO诱导的初始交感神经兴奋，随后使SNA维持在比完整动物更高的水平，这一发现与失血性低血压基本相似[S. Koyama, F. Sawano, Y. Matsuda, Y. Saeki, T. Shibamoto, T. Hayashi, Jr., Y. Matsubayashi, and M. Kawamoto. Am. J. Physiol. 262 (Regulatory Integrative Comp. Physiol. 31): R579-R585, 1992]。在解除VCO后5分钟，压力反射反应性显著减弱：RNA为相应基线的79±11%；CNA为78±8%；HNA为60±16%；SpNA为81±13%。VCO后15分钟，这种减弱消失。迷走神经切断术或静脉注射血管加压素V1受体拮抗剂预处理均可消除这种压力反射减弱。总之，持续10分钟降至50 mmHg的全身性低血压会导致交感压力反射敏感性短暂减弱，这是由于低血压期间心肺感受器卸载释放的循环血管加压素所致。
