Cl- uptake promoting depolarizing GABA actions in immature rat neocortical neurones is mediated by NKCC1
Cl- uptake promoting depolarizing GABA actions in immature rat neocortical neurones is mediated by NKCC1
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DOI：
10.1113/jphysiol.2004.062471
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发表时间：
2004-06-15
影响因子：
5.5
通讯作者：
Fukuda, A
中科院分区：
文献类型：
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作者：
Yamada, J;Okabe, A;Fukuda, A
GABA 是成熟大脑中主要的抑制性神经递质，但在出生后早期发育期间，未成熟新皮质神经元中升高的 [Cl-](i) 导致 GABA(A) 受体激活去极化。这种细胞内 Cl- 积累的分子机制仍然存在争议。因此，通过短杆菌肽穿孔膜片钳方法测量出生后早期大鼠新皮质神经元中的 GABA 逆转电位 (E-GABA) 或 [Cl-](i)，并通过半定量单细胞多重 RT-PCR 检查阳离子-Cl-协同转运蛋白 mRNA（在同一细胞中）的相对表达水平，以寻找与 [Cl-](i)。 mRNA表达水平与[Cl-](i)呈正相关(Cl-积累Na+,K+-2Cl(-)协同转运蛋白NKCC1)或负相关(Cl-挤出K+-Cl-协同转运蛋白KCC2)。 NKCC1 mRNA 表达在出生后早期较高，但在出生后发育过程中下降，而 KCC2 mRNA 表达则表现出相反的模式。皮质板 (CP) 神经元中的 [Cl-](i) 和 NKCC1 mRNA 表达均高于给定切片中可能较老的 V/VI 层锥体神经元。布美他尼对EGABA的药理作用与NKCC1 mRNA的不同表达水平一致。这些数据表明，NKCC1可能在未成熟CP细胞中GABA介导的去极化的产生中发挥关键作用，而KCC2则促进大鼠新皮质中GABA能抑制的后期成熟。
GABA is the principal inhibitory neurotransmitter in the mature brain, but during early postnatal development the elevated [Cl-](i) in immature neocortical neurones causes GABA(A) receptor activation to be depolarizing. The molecular mechanisms underlying this intracellular Cl- accumulation remain controversial. Therefore, the GABA reversal potential (E-GABA) or [Cl-](i) in early postnatal rat neocortical neurones was measured by the gramicidin-perforated patch-clamp method, and the relative expression levels of the cation-Cl- cotransporter mRNAs (in the same cells) were examined by semiquantitative single-cell multiplex RT-PCR to look for statistical correlations with [Cl-](i). The mRNA expression levels were positively (the Cl- accumulating Na+,K+-2Cl(-) cotransporter NKCC1) or negatively (the Cl- extruding K+-Cl- cotransporter KCC2) correlated with [Cl-](i). NKCC1 mRNA expression was high in early postnatal days, but decreased during postnatal development, whereas KCC2 mRNA expression displayed the opposite pattern. [Cl-](i) and NKCC1 mRNA expression were each higher in cortical plate (CP) neurones than in the presumably older layer V/VI pyramidal neurones in a given slice. The pharmacological effects of bumetanide on EGABA were consistent with the different expression levels of NKCC1 mRNA. These data suggest that NKCC1 may play a pivotal role in the generation of GABA-mediated depolarization in immature CP cells, while KCC2 promotes the later maturation of GABAergic inhibition in the rat neocortex.