Although diverse effects of volatile anesthetics have been investigated in various studies, the mechanisms of action of such anesthetics, especially sevoflurane, remain elusive. In contrast to their potent modulation of inhibitory synaptic transmission there is little information about their effects on excitatory transmission in the brain. In this study, we examined the effect of sevoflurane on the excitatory synaptic transmission at CA1 synapses in hippocampal slices of mice. Sevoflurane at 5% was mixed with 95% O2 and 5% CO2 and bubbled in artificial cerebral spinal fluid (0.69 mM). Extracellular recordings of the field excitatory postsynaptic potential (fEPSP) and presynaptic fiber volley (FV) were made at physiological temperature. In addition, fluorescent measurements of presynaptic Ca2+ transients were performed while simultaneously recording fEPSP. Application of sevoflurane reduced the amplitude of fEPSP (45 ± 8%, n = 5). This effect was accompanied by concurrent enhancement of the paired-pulse facilitation of fEPSP (127 ± 5%, n = 12), suggesting a possible presynaptic site of action of sevoflurane. The amplitude of FV was not significantly affected (102 ± 5%, n = 5). In contrast, fluorescent measurements revealed that presynaptic Ca2+ influx was suppressed by sevoflurane (69 ± 5%, n = 7), as was simultaneously recorded fEPSP (44 ± 5%, n = 7). Our results suggest that sevoflurane potently suppresses excitatory synaptic transmission via inhibition of presynaptic Ca2+ influx without affecting presynaptic action potentials.

中文翻译：

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七氟醚可抑制突触前钙流入，而不会影响海马CA1区的突触前动作电位。

尽管在各种研究中已经研究了挥发性麻醉剂的多种作用，但是这种麻醉剂，特别是七氟醚的作用机理仍然难以捉摸。与它们对抑制性突触传递的有效调节相反，关于它们对大脑兴奋性传递的影响的信息很少。在这项研究中，我们检查了七氟醚对小鼠海马切片CA1突触处兴奋性突触传递的影响。将5％的七氟醚与95％的O2和5％的CO2混合，并在人工脑脊髓液（0.69 mM）中鼓泡。在生理温度下记录野外兴奋性突触后电位（fEPSP）和突触前纤维齐射（FV）的细胞外记录。此外，进行突触前Ca2 +瞬变的荧光测量，同时记录fEPSP。七氟醚的应用降低了fEPSP的幅度（45±8％，n = 5）。这种作用伴随着同时增强fEPSP的成对脉冲促进作用（127±5％，n = 12），表明七氟醚的可能的突触前作用位点。FV的幅度没有受到显着影响（102±5％，n = 5）。相反，荧光测量显示，七氟醚抑制了突触前Ca2 +的流入（69±5％，n = 7），同时记录了fEPSP（44±5％，n = 7）。我们的结果表明，七氟醚通过抑制突触前Ca2 +内流而有效抑制兴奋性突触传递，而不会影响突触前动作电位。七氟醚的应用降低了fEPSP的幅度（45±8％，n = 5）。这种作用伴随着同时增强fEPSP的成对脉冲促进作用（127±5％，n = 12），表明七氟醚的可能的突触前作用位点。FV的幅度没有受到显着影响（102±5％，n = 5）。相反，荧光测量显示，七氟醚抑制了突触前Ca2 +的流入（69±5％，n = 7），同时记录了fEPSP（44±5％，n = 7）。我们的结果表明，七氟醚通过抑制突触前Ca2 +内流而有效抑制兴奋性突触传递，而不会影响突触前动作电位。七氟醚的应用降低了fEPSP的幅度（45±8％，n = 5）。这种作用伴随着同时增强fEPSP的成对脉冲促进作用（127±5％，n = 12），表明七氟醚的可能的突触前作用位点。FV的幅度没有受到显着影响（102±5％，n = 5）。相反，荧光测量显示，七氟醚抑制了突触前Ca2 +的流入（69±5％，n = 7），同时记录了fEPSP（44±5％，n = 7）。我们的结果表明，七氟醚通过抑制突触前Ca2 +内流而有效抑制兴奋性突触传递，而不会影响突触前动作电位。提示七氟醚的可能的突触前作用部位。FV的幅度没有受到显着影响（102±5％，n = 5）。相反，荧光测量显示，七氟醚抑制了突触前Ca2 +的流入（69±5％，n = 7），同时记录了fEPSP（44±5％，n = 7）。我们的结果表明，七氟醚通过抑制突触前Ca2 +内流而有效抑制兴奋性突触传递，而不会影响突触前动作电位。提示七氟醚的可能的突触前作用部位。FV的幅度没有受到显着影响（102±5％，n = 5）。相反，荧光测量显示，七氟醚抑制了突触前Ca2 +的流入（69±5％，n = 7），同时记录了fEPSP（44±5％，n = 7）。我们的结果表明，七氟醚通过抑制突触前Ca2 +内流而有效抑制兴奋性突触传递，而不会影响突触前动作电位。