Molecular mechanism of anesthesia of xenon : specific or nonspecific effect?

1)用X射线衍射法研究挥发性麻醉药与紫膜的结合，将浓缩的紫膜悬浮液密封在直径为1 mm的玻璃毛细管中，毛细管两侧还包括含有或不含有挥发性麻醉剂和二碘甲烷的缓冲溶液。将X射线衍射图记录在成像板上，并由图像扫描仪读取。2)氙气、一氧化二氮和挥发性麻醉剂对异型红细胞表达重组GABAA受体和重组NMDAA受体的影响。将编码α-1、β-2和γ-2S GABAA受体亚基以及ζ-1、ε-1受体的cDNA亚克隆到转录载体中。用适当的限制性内切酶将含有每个亚基的载体线性化，以产生模板cDNA，并在体外合成了cRNA。将不同的GABA_A受体亚基(α_1、β_2和α_1、β_2、γ_2s)和N-甲基-D-天冬氨酸受体(ζ_1、ε_1)注射到爪哇卵母细胞，在20℃孵育48h。电生理记录采用双电极电压钳技术。挥发性麻醉剂对α-1-β-2和α-1-β-2-γ-2s受体产生的电流有剂量依赖性增强作用，而氙气和一氧化二氮则无明显增强作用。相反，挥发性麻醉剂不影响ζ-1-ε-1受体的电流，而氙气和一氧化二氮呈剂量依赖性地抑制该电流。结果提示，惰性气体氙气以特定方式作用于神经元受体。

1) Binding of volatile anesthetics to purple membranes studied by X-ray diffraction.The concentrated purple membranes suspension was sealed in a 1 mm diameter glass capillary which also included buffer solution with or without volatile anesthetic, diiodomethane at its both sides. The X-ray diffraction pattern was recorded on a imaging plate and read by an image scanner. The X-ray diffraction study showed that anesthetics bound specifically to the protein-lipid interfacial region within a trimer near the surface of bacteriorhodopsin in the purple membrane.2) Effects of xenon, nitrous oxide and volatile anesthetics on recombinant GABA_A receptors and recombinant NMDA receptors expressing in Xenopusoocyte.Mouse cDNAs encoding for α1, β2 and γ2s GABA_A receptor subunits, and for ζ1, ε1 NMDA receptor were subcloned into transcription vector. A vector containing each subunit was linearized by an appropriate restriction enzyme to create the template cDNA and cRNA was synthesized in vitro. Different combinations of GABA_A receptor subunits (α1 β2 and α1 β2 γ2s ) and NMDA receptor (ζ1 ε1) were injected to Xenopusoocyte followed by incubation at 20℃ for >48h. The electrophysiological recordings were made by using the two electrode-voltage clamp technique. Volatile anesthetics potentiated GABA-induced current in dose dependent manners in the α1 β2 and α1 β2 γ2s receptors, but xenon and nitrous oxide showed no significant potentiation. On the contrary, volatile anesthetics did not affect NMDA-induced current in the ζ1 ε1 recentor, but xenon and nitrous oxide depressed it dose-dependently.The results suggest that an inert gas, xenon acts on neuronal receptors in the specific manner.