Inhibition of presynaptic sodium channels by halothane
Inhibition of presynaptic sodium channels by halothane
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DOI：
10.1097/00000542-199804000-00025
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发表时间：
1998-04-01
期刊：
影响因子：
8.8
通讯作者：
Hemmings, HC
中科院分区：
文献类型：
--
作者：
Ratnakumari, L;Hemmings, HC
背景资料：最近的电生理学研究表明，临床浓度的挥发性全身麻醉剂抑制中枢神经系统钠（Na+）通道。本研究利用大鼠脑突触体测定氟烷对Na+通道功能的生化影响（夹断神经末梢）来评估突触前Na+通道在麻醉效果中的作用。用成年大鼠大脑皮层突触体观察氟烷对藜芦碱诱发的Na ~+通道依赖性Na ~+内流的影响（使用Na-22（+））、突触体内[Na+]的变化（使用离子特异性荧光分光光度法）和神经毒素与Na+通道的特异性受体位点的相互作用（通过放射性配体结合）。通过测量氟烷对藜芦碱诱发的Na+通道依赖性谷氨酸释放的影响，确定这些作用的潜在生理和功能意义（使用酶联荧光分光光度法）。氟烷抑制藜芦碱诱发的Na-22（+）内流（IC 50 = 1.1 mM）和突触体内[Na+]的变化（50%抑制浓度[IC 50] = 0.97 mM），并且它特异性地拮抗[H-3] Batrachotoxin-A 20-alpha-benzoate与Na+通道的受体位点2的结合（IC 50 = 0.53 mM）。Scatchard和动力学分析揭示了抑制毒素结合的变构竞争机制。氟烷抑制藜芦碱诱发的谷氨酸释放突触体具有可比的效力（IC 50 = 0.67 mM）。结论：氟烷显着抑制Na+通道介导的Na+内流，增加突触体内[Na+]和谷氨酸释放，并竞争与神经毒素结合到站点2的Na+通道在突触体在其临床范围内的浓度（最小肺泡浓度，1-2）。这些发现支持突触前Na+通道作为全身麻醉作用的分子靶点的作用。
Background: Recent electrophysiologic studies indicate that clinical concentrations of volatile general anesthetic agents inhibit central nervous system sodium (Na+) channels. In this study, the biochemical effects of halothane on Na+ channel function were determined using rat brain synaptosomes (pinched-off nerve terminals) to assess the role of presynaptic Na+ channels in anesthetic effects.Methods: Synaptosomes from adult rat cerebral cortex were used to determine the effects of halothane on veratridine-evoked Na+ channel-dependent Na+ influx (using Na-22(+)), changes in intrasynaptosomal [Na+] (using ion-specific spectrofluorometry), and neurotoxin interactions with specific receptor sites of the Na+ channel (by radioligand binding). The potential physiologic and functional significance of these effects was determined by measuring the effects of halothane on veratridine-evoked Na+ channel-dependent glutamate release (using enzyme-coupled spectrofluorometry).Results: Halothane inhibited veratridine-evoked Na-22(+) influx (IC50 = 1.1 mM) and changes in intrasynaptosomal [Na+] (concentration for 50% inhibition [IC50] = 0.97 mM), and it specifically antagonized [H-3]batrachotoxinin-A 20-alpha-benzoate binding to receptor site two of the Na+ channel (IC50 = 0.53 mM). Scatchard and kinetic analysis revealed an allosteric competitive mechanism for inhibition of toxin binding. Halothane inhibited veratridine-evoked glutamate release from synaptosomes with comparable potency (IC50 = 0.67 mM).Conclusions: Halothane significantly inhibited Na+ channel-mediated Na+ influx, increases in intrasynaptosomal [Na+] and glutamate release, and competed with neurotoxin binding to site two of the Na+ channel in synaptosomes at concentrations within its clinical range (minimum alveolar concentration, 1-2). These findings support a role for presynaptic Na+ channels as a molecular target for general anesthetic effects.