Chen Y H, Blair M L, Izzo J L
J Auton Nerv Syst. 1984 Nov;11(3):285-95. doi: 10.1016/0165-1838(84)90042-0.
These experiments were designed to determine if renal venous norepinephrine (NE) overflow provides a valid index of renal sympathetic nerve activity. In addition, we evaluated the effect of beta-adrenoceptor blockade on renal NE overflow during graded renal nerve stimulation in order to examine the possibility that presynaptic beta-adrenoceptors facilitate neuronal release of NE in the kidney. In 6 pentobarbital-anesthetized dogs, the renal nerves were transected to remove tonic nerve activity and the distal ends were electrically stimulated (8-25 V, 0.5 ms) over the range of 0.3-5.0 Hz for consecutive 4-min periods. NE overflow rate was calculated as the product of the veno-arterial NE concentration difference and renal plasma flow. Control values of NE overflow (-8.7 +/- 1.8 ng/min) demonstrated net clearance of NE from the renal circulation. NE overflow rate rose to -3.1 +/- 2.2, 1.0 +/- 4.0, and 33.2 +/- 15.4 ng/min at 0.3, 0.6, and 1.2 Hz stimulation, respectively, with no accompanying change in renal blood flow. At 2.4 and 5.0 Hz, renal blood flow decreased by 21 +/- 4% and 37 +/- 3%, but there was no further increase in NE overflow rate (38.8 +/- 9.4 and 27.8 +/- 6.5 ng/min). Propranolol (0.5-1.0 mg . kg-1 plus 0.4-0.5 mg . kg-1 i.v., n = 4) did not alter the effect of nerve stimulation on either NE overflow or renal blood flow. Thus we were unable to demonstrate the presence of functional renal presynaptic beta-adrenoceptors. Further, our data indicate that renal norepinephrine overflow rate is not always a reliable index of renal nerve activity, since NE overflow was not proportional to renal nerve stimulation rate at frequencies high enough to cause vasoconstriction.
这些实验旨在确定肾静脉去甲肾上腺素（NE）溢出是否能提供肾交感神经活动的有效指标。此外，我们评估了β-肾上腺素能受体阻断对分级肾神经刺激期间肾NE溢出的影响，以研究突触前β-肾上腺素能受体促进肾脏中NE神经元释放的可能性。在6只戊巴比妥麻醉的犬中，切断肾神经以消除紧张性神经活动，并在连续4分钟内以0.3 - 5.0Hz的频率对远端进行电刺激（8 - 25V，0.5ms）。NE溢出率通过静脉-动脉NE浓度差与肾血浆流量的乘积来计算。NE溢出的对照值（-8.7±1.8ng/min）表明肾循环中NE有净清除。在0.3、0.6和1.2Hz刺激时，NE溢出率分别升至-3.1±2.2、1.0±4.0和33.2±15.4ng/min，肾血流量无伴随变化。在2.4和5.0Hz时，肾血流量分别下降21±4%和37±3%，但NE溢出率无进一步增加（38.8±9.4和27.8±6.5ng/min）。普萘洛尔（0.5 - 1.0mg·kg-1静脉注射加0.4 - 0.5mg·kg-1静脉注射，n = 4）未改变神经刺激对NE溢出或肾血流量的影响。因此，我们无法证明功能性肾突触前β-肾上腺素能受体的存在。此外，我们的数据表明，肾去甲肾上腺素溢出率并不总是肾神经活动的可靠指标，因为在足以引起血管收缩的频率下，NE溢出与肾神经刺激率不成比例。
