1UCL School of Pharmacy University College London, London, WC1N 1AX UK.
2Institute of Biophysics, National Research Council, 90146 Palermo, Italy.
Commun Biol. 2019 Apr 26;2:145. doi: 10.1038/s42003-019-0408-4. eCollection 2019.
Little is known about the properties and function of ion channels that affect synaptic terminal-resting properties. One particular subthreshold-active ion channel, the Kv7 potassium channel, is highly localized to axons, but its role in regulating synaptic terminal intrinsic excitability and release is largely unexplored. Using electrophysiological recordings together with computational modeling, we found that the K7 current was active at rest in adult hippocampal mossy fiber synaptic terminals and enhanced their membrane conductance. The current also restrained action potential-induced Ca influx via N- and P/Q-type Ca channels in boutons. This was associated with a substantial reduction in the spike half-width and afterdepolarization following presynaptic spikes. Further, by constraining spike-induced Ca influx, the presynaptic K7 current decreased neurotransmission onto CA3 pyramidal neurons and short-term synaptic plasticity at the mossy fiber-CA3 synapse. This is a distinctive mechanism by which K7 channels influence hippocampal neuronal excitability and synaptic plasticity.
关于影响突触末梢静息特性的离子通道的特性和功能，人们知之甚少。一种特殊的亚阈激活离子通道，Kv7 钾通道，高度局限于轴突，但它在调节突触末梢固有兴奋性和释放中的作用在很大程度上尚未被探索。我们使用电生理记录和计算建模发现，Kv7 电流在成年海马苔藓纤维突触末梢的静息状态下是活跃的，并增强了它们的膜电导。该电流还通过 N-型和 P/Q-型钙通道在末梢球内限制动作电位诱导的 Ca 内流。这与突触前尖峰后去极化和半宽的显著减少有关。此外，通过限制尖峰诱导的 Ca 内流，Kv7 电流减少了 CA3 锥体神经元上的神经递质传递和苔藓纤维-CA3 突触的短期突触可塑性。这是 Kv7 通道影响海马神经元兴奋性和突触可塑性的一种独特机制。
