Department of Biochemistry and Biophysics, Faculty of Natural Sciences, Vilnius University, Ciurlionio 21, LT-03101 Vilnius, Lithuania.
Brain Res. 2011 Feb 10;1373:11-6. doi: 10.1016/j.brainres.2010.12.011. Epub 2010 Dec 11.
Voltage dependent ion channels can influence signal integration in neurons dramatically. In addition to the classical fast-inactivating Na(+) current that mediates action potentials, many neurons also express persistent sodium current (I(NaP)). Activating at membrane potentials below the threshold for action potentials, this current may amplify excitatory postsynaptic potentials and shape the firing patterns. To determine the qualitative contribution of I(NaP) to the intrinsic firing properties of motoneurons, we eliminated this current by dynamic clamp. As expected, we found that elimination of I(NaP) shifted the rheobase to more positive currents. More interestingly, elimination of I(NaP) increased the steepness of initial frequency-to-current (fI) relation. This suggests that I(NaP) decreases the transient gain and broadens the integration window for short synaptic inputs in spinal motoneurons.
电压门控离子通道可以显著影响神经元中的信号整合。除了介导动作电位的经典快速失活钠电流外，许多神经元还表达持续钠电流（I(NaP)）。该电流在动作电位阈值以下的膜电位下激活，可能会放大兴奋性突触后电位并形成放电模式。为了确定 I(NaP)对运动神经元固有放电特性的定性贡献，我们通过动态钳位消除了这种电流。正如预期的那样，我们发现消除 I(NaP)会将兴奋阈移至更正的电流。更有趣的是，消除 I(NaP)增加了初始频率-电流（fI）关系的陡峭度。这表明 I(NaP)降低了脊髓运动神经元中短突触输入的瞬态增益并拓宽了整合窗口。
