Dynamic control of presynaptic ca2+inflow by fast-inactivating K+ channels in hippocampal mossy fiber boutons
Dynamic control of presynaptic ca2+inflow by fast-inactivating K+ channels in hippocampal mossy fiber boutons
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DOI：
10.1016/s0896-6273(00)00164-1
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发表时间：
2000-12-01
期刊：
影响因子：
16.2
通讯作者：
Jonas, P
中科院分区：
文献类型：
--
作者：
Geiger, JRP;Jonas, P
在皮质突触中，突触强度的突触前决定因素的分析一直很困难，主要是由于缺乏直接接触突触前元件的途径。在这里，我们报告膜片钳记录苔藓纤维扣（MFB）在大鼠海马脑片。突触前动作电位在低频刺激期间非常短，但在高频刺激期间延长高达3倍。电压门控性K+通道在MFB中失活迅速，但从失活中恢复非常缓慢，表明累积的K+通道失活介导活性依赖性峰加宽。突触前电压波形的延长导致每个动作电位进入终端的Ca 2+离子的数量增加，并在MFB-CA 3锥体细胞突触诱发兴奋性突触后电流的连续增强。因此，突触前K+通道的失活有助于控制皮层中的突触能突触的功效。
Analysis of presynaptic determinants of synaptic strength has been difficult at cortical synapses, mainly due to the lack of direct access to presynaptic elements. Here we report patch-clamp recordings from mossy fiber boutons (MFBs) in rat hippocampal slices. The presynaptic action potential is very short during low-frequency stimulation but is prolonged up to 3-fold during high-frequency stimulation. Voltage-gated K+ channels in MFBs inactivate rapidly but recover from inactivation very slowly, suggesting that cumulative K+ channel inactivation mediates activity-dependent spike broadening. Prolongation of the presynaptic voltage waveform leads to an increase in the number of Ca2+ ions entering the terminal per action potential and to a consecutive potentiation of evoked excitatory postsynaptic currents at MFB-CA3 pyramidal cell synapses. Thus, inactivation of presynaptic K+ channels contributes to the control of efficacy of a glutamatergic synapse in the cortex.