Ransdell Joseph L, Dranoff Edward, Lau Brandon, Lo Wan-Lin, Donermeyer David L, Allen Paul M, Nerbonne Jeanne M
Departments of Developmental Biology and Internal Medicine , Washington University School of Medicine, St. Louis, MO 63110, USA.
Department of Pathology and Immunology , Washington University School of Medicine, St. Louis, MO 63110, USA.
Cell Rep. 2017 Apr 18;19(3):532-544. doi: 10.1016/j.celrep.2017.03.068.
The resurgent component of voltage-gated Na (Nav) currents, I, has been suggested to provide the depolarizing drive for high-frequency firing and to be generated by voltage-dependent Nav channel block (at depolarized potentials) and unblock (at hyperpolarized potentials) by the accessory Navβ4 subunit. To test these hypotheses, we examined the effects of the targeted deletion of Scn4b (Navβ4) on I and on repetitive firing in cerebellar Purkinje neurons. We show here that Scn4b animals have deficits in motor coordination and balance and that firing rates in Scn4b Purkinje neurons are markedly attenuated. Acute, in vivo short hairpin RNA (shRNA)-mediated "knockdown" of Navβ4 in adult Purkinje neurons also reduced spontaneous and evoked firing rates. Dynamic clamp-mediated addition of I partially rescued firing in Scn4b Purkinje neurons. Voltage-clamp experiments revealed that I was reduced (by ∼50%), but not eliminated, in Scn4b Purkinje neurons, revealing that additional mechanisms contribute to generation of I.
电压门控钠（Nav）电流的复苏成分I，被认为可为高频放电提供去极化驱动力，并且是由辅助性Navβ4亚基在去极化电位下对Nav通道进行电压依赖性阻断以及在超极化电位下解除阻断所产生的。为了验证这些假设，我们研究了靶向敲除Scn4b（Navβ4）对小脑浦肯野神经元中I及重复放电的影响。我们在此表明，Scn4b基因敲除动物存在运动协调和平衡缺陷，且Scn4b浦肯野神经元的放电频率明显降低。在成年浦肯野神经元中，通过急性体内短发夹RNA（shRNA）介导的Navβ4“敲低”也降低了自发和诱发的放电频率。动态钳介导的I的添加部分挽救了Scn4b浦肯野神经元的放电。电压钳实验表明，Scn4b浦肯野神经元中的I降低了（约50%），但并未消除，这表明还有其他机制参与I的产生。
