Jurd Rachel, Arras Margarete, Lambert Sachar, Drexler Berthold, Siegwart Roberta, Crestani Florence, Zaugg Michael, Vogt Kaspar E, Ledermann Birgit, Antkowiak Bernd, Rudolph Uwe
Institute of Pharmacology and Toxicology, University of Zürich, CH-8057 Zürich, Switzerland.
FASEB J. 2003 Feb;17(2):250-2. doi: 10.1096/fj.02-0611fje. Epub 2002 Dec 3.
General anesthetics are widely used in clinical practice. On the molecular level, these compounds have been shown to modulate the activity of various neuronal ion channels. However, the functional relevance of identified sites in mediating essential components of the general anesthetic state, such as immobility and hypnosis, is still unknown. Using gene-targeting technology, we generated mice harboring a subtle point mutation (N265M) in the second transmembrane region of the beta3 subunit of the GABA(A) receptor. In these mice, the suppression of noxious-evoked movements in response to the intravenous anesthetics etomidate and propofol is completely abolished, while only slightly decreased with the volatile anesthetics enflurane and halothane. beta3(N265M) mice also display a profound reduction in the loss of righting reflex duration in response to intravenous but not volatile anesthetics. In addition, electrophysiological recordings revealed that anesthetic agents were significantly less effective in enhancing GABA(A) receptor-mediated currents, and in decreasing spontaneous action potential firing in cortical brain slices derived from mutant mice. Taken together, our results demonstrate that a single molecular target, and indeed a specific residue (N265) located within the GABA(A) receptor beta3 subunit, is a major determinant of behavioral responses evoked by the intravenous anesthetics etomidate and propofol, whereas volatile anesthetics appear to act via a broader spectrum of molecular targets.
全身麻醉剂在临床实践中广泛应用。在分子水平上，这些化合物已被证明可调节各种神经元离子通道的活性。然而，已确定的位点在介导全身麻醉状态的基本组成部分（如不动和催眠）中的功能相关性仍不清楚。利用基因靶向技术，我们培育出了在GABA(A)受体β3亚基的第二个跨膜区域存在微小点突变（N265M）的小鼠。在这些小鼠中，对静脉麻醉剂依托咪酯和丙泊酚产生的有害诱发运动的抑制作用完全消失，而对挥发性麻醉剂恩氟烷和氟烷的抑制作用仅略有降低。β3（N265M）小鼠对静脉麻醉剂而非挥发性麻醉剂产生的翻正反射持续时间丧失也有显著降低。此外，电生理记录显示，麻醉剂在增强GABA(A)受体介导的电流以及减少来自突变小鼠的皮质脑片中的自发动作电位发放方面效果明显较差。综上所述，我们的结果表明，单个分子靶点，实际上是位于GABA(A)受体β3亚基内的一个特定残基（N265），是静脉麻醉剂依托咪酯和丙泊酚诱发行为反应的主要决定因素，而挥发性麻醉剂似乎通过更广泛的分子靶点起作用。
