Deletion of the GABAA receptor α1 subunit increases tonic GABAA receptor current:: A role for GABA uptake transporters
Deletion of the GABAA receptor α1 subunit increases tonic GABAA receptor current:: A role for GABA uptake transporters
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DOI：
10.1523/jneurosci.2610-06.2006
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发表时间：
2006-09-06
影响因子：
5.3
通讯作者：
Vicini, Stefano
中科院分区：
文献类型：
--
作者：
Ortinski, Pavel I.;Turner, Jill R.;Vicini, Stefano
缺乏 GABA(A) α 1 亚基基因的小鼠失去了一半以上的 GABA(A) 受体，但缺乏明显的表型，这有点矛盾。我们探索了强直 GABA(A) 受体介导的电流作为 α 1 敲除 (-/-) 小鼠补偿调节目标的作用。与野生型 (-/-) 小鼠相比，α 1 -/- 小鼠的小脑颗粒细胞 (CGC) 的强直电流增加了 62%，基线电流方差增加了 67%。对低浓度 GABA 和 4,5,6,7-四氢异恶唑并[5,4-c]吡啶-3-ol 引起的全细胞电流的检查表明，α 1 -/- 中含有 α 6 和 δ 亚基的 GABAA 受体没有上调，这证实了之前的生化研究。 α 1 -/- 神经元的单通道电流开口平均缩短 32%。单通道电导和开放频率在基因型之间没有差异。应用 GABA 转运蛋白 GAT-1 阻断剂 NO711 (1-[ 2([(二苯基亚甲基)亚氨基]氧基)乙基]-1,2,5,6-四氢3-吡啶甲酸盐酸盐)诱导的强直电流在 α 1 -/- 中显着更大，表明环境 GABA 浓度增加。使用已知浓度的细胞外 GABA 进行的实验，辅之以一系列生化实验，揭示了 alpha 1 -/- 中 GAT 活性的降低，而 GAT-1 或 GAT-3 蛋白没有明显的减少。我们报告了 α1-/-CGC 中 GABAA 受体介导的强直电流增加作为一种新的补偿机制。我们的数据确立了 GABA 转运蛋白在该模型和相关模型中作为神经元兴奋性调节剂的作用，并检查了负责小脑网络对主要突触 GABAA 受体亚基缺失的适应性反应的其他强直电导调节机制。
The loss of more than half the number of GABA(A) receptors yet lack of pronounced phenotype in mice lacking the gene for the GABA(A) alpha 1 subunit is somewhat paradoxical. We explored the role of tonic GABA(A) receptor-mediated current as a target of compensatory regulation in the alpha 1 knock-out (-/-) mice. A 62% increase of tonic current was observed in the cerebellar granule cells (CGCs) of alpha 1 -/-compared with wild-type (-/-) mice along with a 67% increase of baseline current variance. Examination of whole-cell currents evoked by low concentrations of GABA and 4,5,6,7-tetrahydroisoxazolo[ 5,4-c] pyridin-3-ol suggested no upregulation of alpha 6 and delta subunit-containing GABAA receptors in the alpha 1 -/-, confirming previous biochemical studies. Single-channel current openings were on average 32% shorter in the alpha 1 -/-neurons. Single-channel conductance and frequency of opening were not different between genotypes. Tonic current induced by application of the GABA transporter GAT-1 blocker NO711 (1-[ 2([(diphenylmethylene) imino] oxy) ethyl]-1,2,5,6-tetrahydro3-pyridinecarboxylic acid hydrochloride) was significantly larger in the alpha 1 -/-, suggesting an increase of ambient GABA concentration. Experiments done with a known concentration of extracellular GABA complemented by a series of biochemical experiments revealed a reduction of GAT activity in alpha 1 -/-without an identifiable reduction of GAT-1 or GAT-3 protein. We report increased tonic GABAA receptor-mediated current in the alpha 1 -/-CGCs as a novel compensatory mechanism. Our data establish a role for GABA transporters as regulators of neuronal excitability in this and relevant models and examine other tonic conductance-regulating mechanisms responsible for the adaptive response of the cerebellar network to a deletion of a major synaptic GABAA receptor subunit.