Guan Dongxu, Pathak Dhruba, Foehring Robert C
Department of Anatomy and Neurobiology, University of Tennessee Health Science Center , Memphis, Tennessee.
J Neurophysiol. 2018 Aug 1;120(2):394-408. doi: 10.1152/jn.00691.2017. Epub 2018 Apr 11.
We used voltage-clamp recordings from somatic outside-out macropatches to determine the amplitude and biophysical properties of putative Kv1-mediated currents in layer 5 pyramidal neurons (PNs) from mice expressing EGFP under the control of promoters for etv1 or glt. We then used whole cell current-clamp recordings and Kv1-specific peptide blockers to test the hypothesis that Kv1 channels differentially regulate action potential (AP) voltage threshold, repolarization rate, and width as well as rheobase and repetitive firing in these two PN types. We found that Kv1-mediated currents make up a similar percentage of whole cell K current in both cell types, and only minor biophysical differences were observed between PN types or between currents sensitive to different Kv1 blockers. Putative Kv1 currents contributed to AP voltage threshold in both PN types, but AP width and rate of repolarization were only affected in etv1 PNs. Kv1 currents regulate rheobase, delay to the first AP, and firing rate similarly in both cell types, but the frequency-current slope was much more sensitive to Kv1 block in etv1 PNs. In both cell types, Kv1 block shifted the current required to elicit an onset doublet of action potentials to lower currents. Spike frequency adaptation was also affected differently by Kv1 block in the two PN types. Thus, despite similar expression levels and minimal differences in biophysical properties, Kv1 channels differentially regulate APs and repetitive firing in etv1 and glt PNs. This may reflect differences in subcellular localization of channel subtypes or differences in the other K channels expressed. NEW & NOTEWORTHY In two types of genetically identified layer 5 pyramidal neurons, α-dendrotoxin blocked approximately all of the putative Kv1 current (on average). We used outside-out macropatches and whole cell recordings at 33°C to show that despite similar expression levels and minimal differences in biophysical properties, Kv1 channels differentially regulate action potentials and repetitive firing in etv1 and glt pyramidal neurons. This may reflect differences in subcellular localization of channel subtypes or differences in the other K channels expressed.
我们使用来自体细胞外向型大膜片钳的电压钳记录，来确定在etv1或glt启动子控制下表达EGFP的小鼠第5层锥体神经元（PNs）中假定的Kv1介导电流的幅度和生物物理特性。然后，我们使用全细胞电流钳记录和Kv1特异性肽阻断剂，来检验以下假设：Kv1通道在这两种PN类型中对动作电位（AP）电压阈值、复极化速率和宽度以及阈强度和重复放电有不同的调节作用。我们发现，Kv1介导的电流在两种细胞类型中占全细胞K电流的比例相似，并且在PN类型之间或对不同Kv1阻断剂敏感的电流之间仅观察到微小的生物物理差异。假定的Kv1电流在两种PN类型中均对AP电压阈值有贡献，但AP宽度和复极化速率仅在etv1 PNs中受到影响。Kv1电流在两种细胞类型中对阈强度、首次AP延迟和放电频率的调节相似，但频率-电流斜率在etv1 PNs中对Kv1阻断更为敏感。在两种细胞类型中，Kv1阻断均将引发动作电位起始双峰所需的电流转移到更低的电流。两种PN类型中，Kv1阻断对动作电位频率适应的影响也有所不同。因此，尽管表达水平相似且生物物理特性差异极小，但Kv1通道在etv1和glt PNs中对AP和重复放电有不同的调节作用。这可能反映了通道亚型亚细胞定位的差异或所表达的其他K通道的差异。新发现与值得注意之处 在两种基因鉴定的第5层锥体神经元中，α-银环蛇毒素几乎阻断了所有假定的Kv1电流（平均而言）。我们在33°C下使用外向型大膜片钳和全细胞记录表明，尽管表达水平相似且生物物理特性差异极小，但Kv1通道在etv1和glt锥体神经元中对动作电位和重复放电有不同的调节作用。这可能反映了通道亚型亚细胞定位的差异或所表达的其他K通道的差异。
