Park Jinwoo, Galligan James J, Fink Gregory D, Swain Greg M
Department of Chemistry, Department of Pharmacology and Toxicology, and the Neuroscience Program, Michigan State University, East Lansing, Michigan 48824, USA.
Anal Chem. 2006 Oct 1;78(19):6756-64. doi: 10.1021/ac060440u.
Continuous amperometry with a diamond microelectrode and video microscopy were used to record (in vitro) endogenous norepinephrine release simultaneously with the evoked contractile response of a mesenteric artery from a healthy Sprague Dawley rat. Norepinephrine (NE) is a vasoconstricting neurotransmitter released from sympathetic nerves that innervate the smooth muscle cell layers surrounding arteries and veins. Using these two techniques along with several drugs, the NE released at sympathetic neuroeffector junctions nearby the microelectrode was measured as an oxidation current. Key to the amperometric measurement was the use of a diamond microelectrode because of the response sensitivity, reproducibility, and stability it provided. NE release was elicited by electrical stimulation at frequencies between 1 and 60 Hz, with a maximum response seen at 20 Hz. Confirmation that the oxidation current was, in fact, associated with endogenous NE came from the results of several drugs. Tetrodotoxin (TTX, 0.3 microM), a voltage-dependent sodium channel antagonist that blocks nerve conduction, abolished both the oxidation current and the arterial constriction. The alpha(2)-adrenergic autoreceptor antagonist, yohimbine (1.0 microM), caused an increase in the oxidation current and the corresponding constriction. The addition of cocaine (10 microM), an antagonist that inhibits neuronal NE reuptake, caused both the oxidation current and the contractile response to increase. These results, combined with the fact that the hydrodynamic voltammetric E(1/2) for endogenous NE was identical to that for a standard solution, confirmed that the oxidation current was due to NE and that this compound caused, at least in part, the contractile response. The results demonstrate that continuous amperometric monitoring of NE with a diamond microelectrode and video imaging of vascular tone allow real time local measurement of the temporal relationship between nerve-stimulated NE release and arterial constriction.
采用金刚石微电极连续安培法和视频显微镜技术，（在体外）记录健康的斯普拉格 - 道利大鼠肠系膜动脉诱发收缩反应的同时内源性去甲肾上腺素的释放。去甲肾上腺素（NE）是一种从交感神经释放的血管收缩性神经递质，这些交感神经支配着动脉和静脉周围的平滑肌细胞层。使用这两种技术以及几种药物，将微电极附近交感神经效应器连接处释放的NE作为氧化电流进行测量。安培测量的关键在于使用金刚石微电极，因为它具有响应灵敏度、可重复性和稳定性。通过1至60Hz频率的电刺激引发NE释放，在20Hz时观察到最大反应。几种药物的结果证实氧化电流实际上与内源性NE有关。河豚毒素（TTX，0.3 microM）是一种阻断神经传导的电压依赖性钠通道拮抗剂，它消除了氧化电流和动脉收缩。α(2)-肾上腺素能自受体拮抗剂育亨宾（1.0 microM）使氧化电流和相应的收缩增加。添加可卡因（10 microM），一种抑制神经元NE再摄取的拮抗剂，导致氧化电流和收缩反应均增加。这些结果，再加上内源性NE的流体动力伏安法E(1/2)与标准溶液相同这一事实，证实氧化电流是由NE引起的，并且这种化合物至少部分地导致了收缩反应。结果表明，用金刚石微电极连续安培监测NE和血管张力的视频成像可以实时局部测量神经刺激的NE释放与动脉收缩之间的时间关系。
