Altered Responses to Propofol, but Not Ketamine, in Mice Deficient in the 65-Kilodalton Isoform of Glutamate Decarboxylase
Altered Responses to Propofol, but Not Ketamine, in Mice Deficient in the 65-Kilodalton Isoform of Glutamate Decarboxylase
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DOI：
10.1124/jpet.109.151456
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发表时间：
2009-05-01
影响因子：
3.5
通讯作者：
Saito, Shigeru
中科院分区：
文献类型：
--
作者：
Kubo, Kazuhiro;Nishikawa, Koichi;Saito, Shigeru
GABA由谷氨酸脱羧酶（GAD）的两种同工型GAD 65和GAD 67合成。然而，GAD 65介导的GABA合成对麻醉剂体内作用的相对贡献仍然未知。为了解决这个问题，我们使用GAD 65 kDa亚型缺陷的小鼠，并测试了GAD 65缺陷小鼠[GAD 65（-/-）]中GABA含量的部分减少将有助于麻醉剂的催眠和固定作用的假设。比较野生型（WT）小鼠和GAD 65（-/-）小鼠的旷场试验、翻正反射（LORR）丧失、缩尾反应（LTWR）丧失和自发活动。用膜片钳技术观察了全身麻醉药对脑片额叶皮质锥体神经元相性和强直性GABA能电流的影响。丙泊酚（100 mg/kg i.p.）的持续时间-诱导的LORR和丙泊酚（150 mg/kg i.p.）持续时间-与WT小鼠相比，GAD 65（-/-）小鼠中诱导的LTWR显著降低。相比之下，氯胺酮无差异。预先注射GABA转运蛋白1抑制剂NO-711（C21H22N2O3中心点HCl）（0.75 mg/kg i.p.），在GAD 65（-/-）小鼠中恢复丙泊酚的减弱作用。GAD 65（-/-）小鼠的皮质锥体神经元具有较小的强直传导，并且丙泊酚诱导的强直抑制增强小于WT小鼠，这表明GAD 65介导的GABA能抑制张力的基因型差异可能至少部分是行为差异的细胞基础。总之，GAD 65（-/-）小鼠对丙泊酚的反应减弱，但对氯胺酮没有反应，表明GAD 65介导的GABA合成在丙泊酚的催眠和固定作用中起重要作用。
GABA is synthesized by two isoforms of glutamate decarboxylase (GAD), GAD65, and GAD67. However, the relative contributions of GAD65-mediated GABA synthesis to the in vivo actions of anesthetics remain unknown. To address this issue, we used mice deficient in the 65-kDa isoform of GAD and tested the hypothesis that partial reduction of GABA content in GAD65-deficient mice [GAD65(-/-)] would contribute to hypnotic and immobilizing actions of the anesthetics. The open field test, loss of righting reflex (LORR), loss of tail-pinch withdrawal response (LTWR), and locomotor activity were compared between wild-type (WT) mice and GAD65(-/-) mice. Effects of general anesthetics on both phasic and tonic GABAergic currents were examined using the patch-clamp method in frontal cortex pyramidal neurons in brain slices. The duration of propofol (100 mg/kg i.p.)-induced LORR and the duration of propofol (150 mg/kg i.p.)-induced LTWR in GAD65(-/-) mice were significantly reduced compared with WT mice. In contrast, no difference was seen for ketamine. Preinjection of the GABA transporter 1 inhibitor, NO-711 (C21H22N2O3 center dot HCl) (0.75 mg/kg i.p.), reinstated diminished actions of propofol in GAD65(-/-) mice. Cortical pyramidal neurons in GAD65(-/-) mice had smaller tonic conductances, and propofol-induced enhancement of tonic inhibition was smaller than in WT mice, suggesting that genotype differences in GAD65-mediated GABAergic inhibitory tone may be, at least in part, a cellular basis underlying behavioral differences. In conclusion, GAD65(-/-) mice show a diminished response to propofol, but not ketamine, indicating that GAD65-mediated GABA synthesis plays an important role in hypnotic and immobilizing actions of propofol.