Thermal Hyperalgesia via Supraspinal Mechanisms in Mice Lacking Glutamate Decarboxylase 65
Thermal Hyperalgesia via Supraspinal Mechanisms in Mice Lacking Glutamate Decarboxylase 65
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DOI：
10.1124/jpet.109.156034
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发表时间：
2009-10-01
影响因子：
3.5
通讯作者：
Saito, Shigeru
中科院分区：
文献类型：
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作者：
Kubo, Kazuhiro;Nishikawa, Koichi;Saito, Shigeru
由谷氨酸脱羧酶（GAD）的两种亚型合成的γ-氨基丁酸抑制伤害性信号从初级传入纤维向中枢神经系统的传递。然而，GAD（GAD 65）介导的GABA在伤害性加工中的65 kDa亚型的作用尚不清楚。本研究测试了GAD 65基因敲除[GAD 65（-/-）]是否部分降低GABA能抑制性张力有助于调节小鼠的痛阈。在雄性野生型（WT）小鼠和GAD 65（-/-）小鼠上进行实验。在WT小鼠和GAD 65（-/-）小鼠之间比较急性伤害感受和炎性疼痛测试。用全细胞膜片钳技术在脑片体感皮层神经元上观察GABA（A）受体介导的抑制性突触后电流。在反映脊髓上感觉整合的热板测试中，观察到GAD 65（-/-）小鼠的潜伏期显著减少。GABA转运蛋白1抑制剂，1-[2-[[（二苯基亚甲基）亚氨基]氧基]乙基]-1，2，5，6-四氢-3-吡啶羧酸盐酸盐（C21 H22 N2 O3中心点HCl; NO-711）的腹腔内给药，剂量依赖性地延长了两种基因型的潜伏期，表明GABA浓度有助于急性热伤害感受。然而，没有基因型差异的反应，尾部浸泡测试或冯弗雷测试，表明脊髓反射和机械伤害性感受保持完整的GAD 65（-/-）小鼠。对化学性炎症伤害的反应（福尔马林试验和角叉菜胶试验）没有基因型差异。虽然两种基因型的抑制性突触后电流的相位成分的特性相似，但GAD 65（-/-）小鼠的强直抑制显著减少。这些结果支持了GAD 65介导的GABA合成通过脊髓上机制在伤害性处理中起相对较小但重要作用的假设。
gamma-Aminobutyric acid, which is synthesized by two isoforms of glutamate decarboxylase (GAD), inhibits the transfer of nociceptive signals from primary afferent fibers to the central nervous system. However, the roles of a 65-kDa isoform of GAD (GAD65)-mediated GABA in nociceptive processing are less clear. This study tested whether partial reductions in GABAergic inhibitory tone by GAD65 gene knockout [GAD65(-/-)] would contribute to the regulation of pain threshold in mice. Experiments were performed on male wild-type (WT) mice and GAD65(-/-) mice. Acute nociception and inflammatory pain tests were compared between WT mice and GAD65(-/-) mice. GABA(A) receptor-mediated inhibitory postsynaptic currents were also examined by use of the whole-cell patch-clamp method in somatosensory cortical neurons in brain slices. In the hot plate test, which reflects supraspinal sensory integration, a significant reduction in the latency was observed for GAD65(-/-) mice. Intraperitoneal administration of the GABA transporter 1 inhibitor, 1-[2-[[(diphenylmethylene)imino]oxy]ethyl]-1,2,5,6-tetrahydro-3-pyridinecarboxylic acid hydrochloride (C21H22N2O3 center dot HCl; NO-711), dose-dependently prolonged the latency in both genotypes, suggesting that GABA concentration contributes to acute thermal nociception. However, there was no genotype difference in responses to the tail-immersion test or the von Frey test, indicating that spinal reflex and mechanical nociception are kept intact in GAD65(-/-) mice. There was no genotype difference in responses to chemical inflammatory nociception (formalin test and carrageenan test). Although properties of the phasic component of inhibitory postsynaptic currents were similar in both genotypes, tonic inhibition was significantly reduced in GAD65(-/-) mice. These results support the hypothesis that GAD65-mediated GABA synthesis plays relatively small but significant roles in nociceptive processing via supraspinal mechanisms.