The general anesthetic Isoflurane depresses synaptic vesicle exocytosis
The general anesthetic Isoflurane depresses synaptic vesicle exocytosis
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DOI：
10.1124/mol.104.003210
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发表时间：
2005-05-01
影响因子：
3.6
通讯作者：
Ryan, TA
中科院分区：
文献类型：
--
作者：
Hemmings, HC;Yan, W;Ryan, TA
全身麻醉药对突触传递有显着影响，但其突触前作用的机制尚不清楚。我们使用定量激光扫描荧光显微镜来分析挥发性麻醉剂异氟烷对培养的新生大鼠海马神经元突触小泡循环的影响，通过转染与 VAMP（囊泡相关膜蛋白）管腔结构域融合的 pH 敏感形式绿色荧光蛋白进行监测， （突触-pHluorin）或囊泡负载荧光染料 FM 1-43。异氟烷在一定浓度范围内可逆地抑制动作电位诱发的胞吐作用，对囊泡池大小影响很小。相比之下，胞外KCl浓度升高而去极化引起的胞吐作用对选择性Na+通道阻断剂河豚毒素不敏感，对异氟烷相对不敏感。异氟烷对胞吐作用的抑制对荷包牡丹碱具有抗性，表明这种突触前效应不是由挥发性麻醉剂众所周知的 GABA A 受体调节引起的。胞吐作用的抑制通过刺激频率的降低来模拟，表明动作电位的启动、传导或与 Ca2+ 通道激活的耦合减少。没有证据表明对内吞作用有直接影响。因此，异氟烷对突触传递的影响主要是通过抑制 Ca2+ 进入和胞吐作用上游位点的动作电位诱发的突触小泡胞吐作用而引起的，可能是 Na+ 通道阻断和/或 K+ 通道激活的结果，Ca2+ 通道阻断和/或可溶性 N-乙基马来酰亚胺敏感因子附着蛋白的贡献可能较小。 受体介导的囊泡融合。
General anesthetics have marked effects on synaptic transmission, but the mechanisms of their presynaptic actions are unclear. We used quantitative laser-scanning fluorescence microscopy to analyze the effects of the volatile anesthetic isoflurane on synaptic vesicle cycling in cultured neonatal rat hippocampal neurons monitored using either transfection of a pH-sensitive form of green fluorescent protein fused to the luminal domain of VAMP (vesicle-associated membrane protein), (synapto-pHluorin) or vesicle loading with the fluorescent dye FM 1-43. Isoflurane reversibly inhibited action potential-evoked exocytosis over a range of concentrations, with little effect on vesicle pool size. In contrast, exocytosis evoked by depolarization in response to an elevated extracellular concentration of KCl, which is insensitive to the selective Na+ channel blocker tetrodotoxin, was relatively insensitive to isoflurane. Inhibition of exocytosis by isoflurane was resistant to bicuculline, indicating that this presynaptic effect is not caused by the well known GABA A receptor modulation by volatile anesthetics. Depression of exocytosis was mimicked by a reduction in stimulus frequency, suggesting a reduction in action potential initiation, conduction, or coupling to Ca2+ channel activation. There was no evidence for a direct effect on endocytosis. The effects of isoflurane on synaptic transmission are thus caused primarily by inhibition of action potential-evoked synaptic vesicle exocytosis at a site upstream of Ca2+ entry and exocytosis, possibly as a result of Na+ channel blockade and/or K+ channel activation, with the possibility of lesser contributions from Ca2+ channel blockade and/or soluble N-ethylmaleimide-sensitive factor attachment protein receptor-mediated vesicle fusion.