Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.
Neuroscience. 2010 Apr 28;167(1):124-34. doi: 10.1016/j.neuroscience.2010.01.049. Epub 2010 Feb 1.
Radial neuronal migration in the cerebral cortex depends on trophic factors and the activation of different voltage- and ligand-gated channels. To examine the functional role of GABA(C) receptors in radial migration we analyzed the effects of specific GABA(A) and GABA(C) receptor antagonists on the migration of BrdU-labeled neurons in vitro using organotypic neocortical slice cultures. These experiments revealed that the GABA(A) specific inhibitor bicuculline methiodide facilitated neuronal migration, while the GABA(C) specific inhibitor (1,2,5,6-tetrahydropyridine-4-yl) methylphosphinic-acid (TPMPA) impeded migration. Co-application of TPMPA and bicuculline methiodide or the unspecific ionotropic GABA receptor antagonist picrotoxin both impeded migration, suggesting that the GABA(C) receptor mediated effects dominate. Addition of the specific GABA(C) receptor agonist cis-4-aminocrotonic acid (CACA) also hampered migration, indicating that a physiological GABAergic stimulation is required for appropriate function. RT-PCR experiments using specific probes for GABA(C) receptor mRNA and Western blot assays using an antibody directed against rho subunits revealed the expression of GABA(C) receptor mRNA and translated GABA(C) receptor protein in the immature cortex. Microfluorimetric Ca(2+) imaging in neurons of identified cortical layers using Calcium Green revealed the functional expression of GABA(A) and GABA(C) receptors in the intermediate zone, while only GABA(A) receptor mediated responses were observed in the upper cortical plate. In summary, these results demonstrate that activation of GABA(C) receptors is a prerequisite for accurate migration and that GABA(C) receptors are functionally expressed in the intermediate zone.
大脑皮层中的放射状神经元迁移依赖于营养因子和不同电压门控及配体门控通道的激活。为了研究 GABA(C) 受体在放射状迁移中的功能作用，我们分析了特异性 GABA(A) 和 GABA(C) 受体拮抗剂对体外器官型皮质切片培养中 BrdU 标记神经元迁移的影响。这些实验表明，GABA(A) 特异性抑制剂荷包牡丹碱甲碘化物促进神经元迁移，而 GABA(C) 特异性抑制剂 (1,2,5,6-四氢吡啶-4-基) 甲基膦酸 (TPMPA) 则阻碍迁移。TPMPA 和荷包牡丹碱甲碘化物或非特异性离子型 GABA 受体拮抗剂印防己毒素的共同应用均阻碍迁移，表明 GABA(C) 受体介导的作用占主导地位。特异性 GABA(C) 受体激动剂 cis-4-氨基-3-羧基戊酸 (CACA) 的添加也阻碍了迁移，表明适当的功能需要生理性 GABA 能刺激。使用特异性 GABA(C) 受体 mRNA 探针的 RT-PCR 实验和针对 rho 亚基的抗体的 Western blot 分析表明，不成熟皮质中存在 GABA(C) 受体 mRNA 和翻译的 GABA(C) 受体蛋白的表达。使用钙绿在已鉴定的皮质层中的神经元进行微荧光钙成像揭示了中间带中 GABA(A) 和 GABA(C) 受体的功能表达，而仅在皮质上层中观察到 GABA(A) 受体介导的反应。总之，这些结果表明，GABA(C) 受体的激活是准确迁移的前提条件，并且 GABA(C) 受体在中间带中具有功能表达。
