Maiorov D N, Wilton E R, Badoer E, Petrie D, Head G A, Malpas S C
Baker Medical Research Institute, Prahran, P.O. Box 6492, St. Kilda Rd. Central, Melbourne, Victoria 8008, Australia.
Brain Res. 1999 Jan 9;815(2):227-36. doi: 10.1016/s0006-8993(98)01150-0.
Studies in anaesthetized animals have shown that the pontine A5 noradrenergic region plays an important role in the sympathetic control of arterial pressure (AP). The aim of this study was to develop, in conscious rabbits, a technique for microinjections into the A5 region and examine the effects of stimulation of this region on renal sympathetic nerve activity (RSNA). In preliminary mapping experiments on four anaesthetized rabbits, electrical stimulation of the A5 region induced a pressor response ranging between 25 and 75 mmHg while unilateral injection of glutamate (100 nmol) did not change AP. The mapping experiments were used to enable guide cannulae implantation for subsequent microinjections into the A5 region. In six conscious rabbits, unilateral injection of glutamate (100 nmol) caused a consistent increase in RSNA (+45%) but did not change AP. In another eight rabbits, bilateral injection of glutamate (0.3, 3, 30 nmol) into the A5 region dose-dependently increased RSNA by 13%, 30% and 40%, respectively. In four rabbits, angiotensin II (0.3, 3, 30 pmol) injected bilaterally into the A5 region increased RSNA by 5%, 22% and 28%, respectively. In all animals the increase in RSNA was mainly mediated by increasing amplitude of sympathetic synchronized bursts while their frequency remained unchanged. However, both glutamate and angiotensin II did not change AP indicating that the sympathoexcitatory response to the A5 stimulation might be relatively confined to the renal bed. Using a novel microinjection technique developed for conscious rabbits, we found that the A5 region may provide an important excitatory and possibly selective input to the renal sympathetic preganglionic neurons.
对麻醉动物的研究表明，脑桥A5去甲肾上腺素能区域在动脉血压（AP）的交感神经控制中起重要作用。本研究的目的是在清醒兔中开发一种向A5区域进行微量注射的技术，并研究刺激该区域对肾交感神经活动（RSNA）的影响。在对4只麻醉兔进行的初步定位实验中，电刺激A5区域引起的升压反应在25至75 mmHg之间，而单侧注射谷氨酸（100 nmol）并未改变动脉血压。定位实验用于植入引导套管，以便随后向A5区域进行微量注射。在6只清醒兔中，单侧注射谷氨酸（100 nmol）使肾交感神经活动持续增加（+45%），但未改变动脉血压。在另外8只兔中，双侧向A5区域注射谷氨酸（0.3、3、30 nmol），肾交感神经活动分别剂量依赖性增加13%、30%和40%。在4只兔中，双侧向A5区域注射血管紧张素II（0.3、3、30 pmol），肾交感神经活动分别增加5%、22%和28%。在所有动物中，肾交感神经活动的增加主要是通过增加交感神经同步爆发的幅度来介导的，而其频率保持不变。然而，谷氨酸和血管紧张素II均未改变动脉血压，这表明对A5刺激的交感兴奋反应可能相对局限于肾床。使用为清醒兔开发的一种新型微量注射技术，我们发现A5区域可能为肾交感神经节前神经元提供重要的兴奋性且可能是选择性的输入。
