Behar T N, Li Y X, Tran H T, Ma W, Dunlap V, Scott C, Barker J L
Laboratory of Neurophysiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Neurosci. 1996 Mar 1;16(5):1808-18. doi: 10.1523/JNEUROSCI.16-05-01808.1996.
During rat cortical development, when neurons migrate from the ventricular zone to the cortical plate, GABA localizes within the target destinations of migratory neurons. At this time, cells in germinal zones and along migratory pathways express GABA receptor subunit transcripts, implying that in vivo, GABA may be a chemoattractant. We used an in vitro strategy to study putative chemotropic effects of GABA on embryonic rat cortical cells. GABA stimulated neuronal migration in vitro at embryonic day 15 (E15). From E16 onward, two concentration ranges (fM and microM) induced motility. Femtomolar GABA primarily stimulated chemotaxis (migration along a chemical gradient), whereas micromolar GABA predominantly initiated chemokinesis (increased random movement). These effects were mimicked by structural analogs of GABA with relative specificity at GABAA (muscimol), GABAB (R-baclofen), and GABAC (trans- or cis-4-aminocrotonic acid) receptors. Antagonists of GABAB (saclofen) and GABAC (picrotoxin) receptors partially inhibited responses to both femto- and micromolar GABA; however, only responses to femtomolar GABA were partially blocked by bicuculline, a well established antagonist of GABA at GABAA receptors. Hence, chemotactic responses to femtomolar GABA seem to involve all three classes of GABA receptor proteins, whereas chemokinetic responses to micromolar GABA involve GABAB and GABAC receptor proteins. GABA-induced motility was blocked by loading the cells with the Ca(2+)-chelating molecule bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid, suggesting that intracellular Ca2+ mediates GABA-induced cell movement. Optical recordings of cells loaded with Ca2+ indicator dye revealed that both femto- and micromolar GABA evoked increases in intracellular Ca2+. Thus, GABA-stimulated increases in intracellular Ca2+ may mediate both chemotactic and chemokinetic responses in embryonic cortical cells.
在大鼠皮质发育过程中，当神经元从脑室区迁移至皮质板时，GABA定位于迁移神经元的目标目的地内。此时，生发区和沿迁移路径的细胞表达GABA受体亚基转录本，这意味着在体内，GABA可能是一种化学引诱剂。我们采用体外策略研究GABA对胚胎大鼠皮质细胞的假定化学趋向性作用。在胚胎第15天（E15）时，GABA在体外刺激神经元迁移。从E16起，两个浓度范围（飞摩尔和微摩尔）诱导运动性。飞摩尔GABA主要刺激趋化作用（沿化学梯度迁移），而微摩尔GABA主要引发化学增活作用（增加随机运动）。GABA的结构类似物在GABAA（蝇蕈醇）、GABAB（R-巴氯芬）和GABAC（反式或顺式-4-氨基巴豆酸）受体处具有相对特异性，可模拟这些效应。GABAB（沙氯芬）和GABAC（印防己毒素）受体拮抗剂部分抑制对飞摩尔和微摩尔GABA的反应；然而，只有对飞摩尔GABA的反应被荷包牡丹碱部分阻断，荷包牡丹碱是一种在GABAA受体处已确定的GABA拮抗剂。因此，对飞摩尔GABA的趋化反应似乎涉及所有三类GABA受体蛋白，而对微摩尔GABA的化学增活反应涉及GABAB和GABAC受体蛋白。通过用Ca(2+)螯合分子双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸加载细胞，可阻断GABA诱导的运动性，这表明细胞内Ca2+介导GABA诱导的细胞运动。对加载Ca2+指示剂染料的细胞进行光学记录显示，飞摩尔和微摩尔GABA均引起细胞内Ca2+增加。因此，GABA刺激引起的细胞内Ca2+增加可能介导胚胎皮质细胞中的趋化和化学增活反应。
