Merrill D C, McWeeny O J, Segar J L, Robillard J E
Department of Obstetrics and Gynecology, University of Iowa College of Medicine, Iowa City 52242.
Am J Physiol. 1995 Mar;268(3 Pt 2):H1343-51. doi: 10.1152/ajpheart.1995.268.3.H1343.
The present study was designed to characterize the maturation of cardiopulmonary reflex control of renal sympathetic nerve activity (RSNA) independent of influences from the arterial baroreflex. Studies were conducted in conscious newborn lambs (3- to 7-days-old) (n = 16) and older lambs (6- to 8-wk-old) (n = 18). All animals underwent either sinoaortic denervation (SAD) or a sham procedure. Hemodynamic, humoral, neural, and renal responses to volume expansion (6% Dextran 70, 0.7 ml.kg-1.min-1 x 60 min) were recorded. Volume expansion resulted in a significant decrease (P < 0.05) in RSNA in intact newborn (-28.1 +/- 5.3% change from control) and older lambs (-19.4 +/- 10.1%). SAD totally abolished the sympathetic inhibition seen with volume expansion in newborn lambs (-3.6 +/- 5.7%) but not in older lambs (-25.6 +/- 8.4%). Right atrial pressure increased in a similar fashion in both newborn (intact: 5.6 +/- 0.5 mmHg; SAD: 6.1 +/- 0.8 mmHg) and older lambs (intact: 5.2 +/- 0.9 mmHg; SAD: 5.3 +/- 0.9 mmHg) and was not altered by SAD. The reflex bradycardia seen with volume expansion in newborn lambs was blocked by SAD. The present study demonstrates that, during the newborn period, the RSNA and heart rate responses to volume expansion are dependent mainly on the integrity of the arterial baroreflex. Furthermore, these studies suggest that cardiopulmonary reflex control of RSNA in response to volume expansion is impaired early in life and increases with maturation.
本研究旨在表征肾交感神经活动（RSNA）的心肺反射控制的成熟过程，且不受动脉压力反射影响。研究在清醒的新生羔羊（3至7日龄）（n = 16）和较大羔羊（6至8周龄）（n = 18）中进行。所有动物均接受了去窦主动脉神经支配（SAD）或假手术。记录了对容量扩张（6%右旋糖酐70，0.7 ml·kg-1·min-1×60分钟）的血流动力学、体液、神经和肾脏反应。容量扩张导致完整新生羔羊（与对照相比变化-28.1±5.3%）和较大羔羊（-19.4±10.1%）的RSNA显著降低（P < 0.05）。SAD完全消除了新生羔羊容量扩张时出现的交感神经抑制（-3.6±5.7%），但未消除较大羔羊的（-25.6±8.4%）。新生羔羊（完整组：5.6±0.5 mmHg；SAD组：6.1±0.8 mmHg）和较大羔羊（完整组：5.2±0.9 mmHg；SAD组：5.3±0.9 mmHg）的右心房压力以相似方式升高，且不受SAD影响。新生羔羊容量扩张时出现的反射性心动过缓被SAD阻断。本研究表明，在新生儿期，RSNA和心率对容量扩张的反应主要依赖于动脉压力反射的完整性。此外，这些研究表明，对容量扩张的RSNA的心肺反射控制在生命早期受损，并随成熟而增加。
