Martina M, Schultz J H, Ehmke H, Monyer H, Jonas P
Physiologisches Institut der Universität Freiburg, D-79104 Freiburg, Germany.
J Neurosci. 1998 Oct 15;18(20):8111-25. doi: 10.1523/JNEUROSCI.18-20-08111.1998.
We have examined gating and pharmacological characteristics of somatic K+ channels in fast-spiking interneurons and regularly spiking principal neurons of hippocampal slices. In nucleated patches isolated from basket cells of the dentate gyrus, a fast delayed rectifier K+ current component that was highly sensitive to tetraethylammonium (TEA) and 4-aminopyridine (4-AP) (half-maximal inhibitory concentrations <0.1 mM) predominated, contributing an average of 58% to the total K+ current in these cells. By contrast, in pyramidal neurons of the CA1 region a rapidly inactivating A-type K+ current component that was TEA-resistant prevailed, contributing 61% to the total K+ current. Both types of neurons also showed small amounts of the K+ current component mainly found in the other type of neuron and, in addition, a slow delayed rectifier K+ current component with intermediate properties (slow inactivation, intermediate sensitivity to TEA). Single-cell RT-PCR analysis of mRNA revealed that Kv3 (Kv3.1, Kv3.2) subunit transcripts were expressed in almost all (89%) of the interneurons but only in 17% of the pyramidal neurons. In contrast, Kv4 (Kv4.2, Kv4.3) subunit mRNAs were present in 87% of pyramidal neurons but only in 55% of interneurons. Selective block of fast delayed rectifier K+ channels, presumably assembled from Kv3 subunits, by 4-AP reduced substantially the action potential frequency in interneurons. These results indicate that the differential expression of Kv3 and Kv4 subunits shapes the action potential phenotypes of principal neurons and interneurons in the cortex.
我们研究了海马切片中快速发放中间神经元和规则发放的主神经元中体细胞钾离子通道的门控和药理学特性。在从齿状回篮状细胞分离的有核膜片上，一种对四乙铵（TEA）和4-氨基吡啶（4-AP）高度敏感（半数最大抑制浓度<0.1 mM）的快速延迟整流钾电流成分占主导，平均占这些细胞总钾电流的58%。相比之下，在CA1区的锥体细胞中，一种对TEA不敏感的快速失活A型钾电流成分占优势，占总钾电流的61%。这两种类型的神经元还显示出少量主要在另一种类型神经元中发现的钾电流成分，此外，还有一种具有中间特性（缓慢失活、对TEA中等敏感性）的缓慢延迟整流钾电流成分。对mRNA进行单细胞逆转录聚合酶链反应（RT-PCR）分析表明，Kv3（Kv3.1、Kv3.2）亚基转录本在几乎所有（89%）的中间神经元中表达，但仅在17%的锥体细胞中表达。相反，Kv4（Kv4.2、Kv4.3）亚基mRNA存在于87%的锥体细胞中，但仅存在于55%的中间神经元中。4-AP对可能由Kv3亚基组装而成的快速延迟整流钾通道的选择性阻断，显著降低了中间神经元的动作电位频率。这些结果表明，Kv3和Kv4亚基的差异表达塑造了皮层中主神经元和中间神经元的动作电位表型。
