Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE 68198-5850, USA.
J Appl Physiol (1985). 2011 May;110(5):1439-47. doi: 10.1152/japplphysiol.01409.2010. Epub 2011 Feb 3.
We recently reported that reactive oxygen species (ROS) plays an excitatory role in modulation of the exercise pressor reflex (EPR) in normal rats. In this study, we further tested two independent hypotheses: 1) ROS interacts with EPR-related ionotropic receptors such as the purinergic receptors (P(2)) and transient receptor potential vanilloid 1 receptors (TRPV1) to indirectly modulate the EPR function; 2) ROS directly affects excitability of muscle afferents by modulating the voltage-gated sodium (Na(v)) channels. To test the first hypothesis, we performed animal experiments to investigate the effect of the SOD mimetic 4-hydroxy-2,2,6,6-tetramethyl piperidine 1-oxyl (Tempol) on the pressor response to hindlimb intra-arterial (IA) injection of either α,β-methylene ATP (a P(2X) agonist) or capsaicin (a TRPV1 agonist) in decerebrate rats. To test the second hypothesis, we used the patch-clamp technique to determine the effect of ROS on Na(v) channels on the soma of muscle afferents. We also performed local microinjection of a sodium channel blocker, tetrodotoxin (TTX), into ipsilateral L4/L5 dorsal root ganglia (DRGs) to investigate whether the blockade of Na(v) channels by TTX affects the EPR function. We found that Tempol did not affect the pressor response to injection of either capsaicin or α,β-methylene ATP but significantly decreased the Na(v) current in small and medium-sized 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labeled DRG neurons. A membrane-permeant superoxide dismutase, polyethylene glycol (PEG)-SOD, had an effect on the Na(v) current in these neurons similar to that of Tempol. Microinjection of TTX into L4/L5 DRGs dramatically attenuated the pressor response to static contraction induced by electrical stimulation of L4/L5 ventral roots. These data suggest that ROS modulates the EPR by affecting the activity of the Na(v) channels on muscle afferents.
我们最近报道称，活性氧（ROS）在正常大鼠运动加压反射（EPR）的调节中发挥兴奋性作用。在这项研究中，我们进一步验证了两个独立的假设：1）ROS 与 EPR 相关的离子型受体相互作用，如嘌呤能受体（P（2））和瞬时受体电位香草醛 1 型受体（TRPV1），从而间接调节 EPR 功能；2）ROS 通过调节电压门控钠（Na（v））通道直接影响肌传入纤维的兴奋性。为了验证第一个假设，我们进行了动物实验，以研究超氧化物歧化酶模拟物 4-羟基-2,2,6,6-四甲基哌啶 1-氧自由基（Tempol）对去大脑大鼠后肢动脉内（IA）注射α，β-亚甲基 ATP（P2X 激动剂）或辣椒素（TRPV1 激动剂）引起的升压反应的影响。为了验证第二个假设，我们使用膜片钳技术来确定 ROS 对肌传入纤维体上的 Na（v）通道的影响。我们还在同侧 L4/L5 背根神经节（DRG）中局部注射钠通道阻断剂河豚毒素（TTX），以研究 TTX 阻断 Na（v）通道是否会影响 EPR 功能。我们发现 Tempol 不影响注射辣椒素或α，β-亚甲基 ATP 引起的升压反应，但显著降低了小和中大小 1,1'-二辛基-3,3,3',3'-四甲基吲哚羰花青高氯酸盐（DiI）标记的 DRG 神经元中的 Na（v）电流。一种膜通透超氧化物歧化酶，聚乙二醇（PEG）-SOD，对这些神经元中的 Na（v）电流的影响与 Tempol 相似。TTX 注入 L4/L5 DRG 会显著减弱 L4/L5 腹根电刺激引起的静态收缩引起的升压反应。这些数据表明，ROS 通过影响肌传入纤维上的 Na（v）通道活性来调节 EPR。
