Dynamics of excitatory synaptic components in sustained firing at low rates.
Dynamics of excitatory synaptic components in sustained firing at low rates.
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DOI：
10.1152/jn.00530.2004
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发表时间：
2005-06
影响因子：
2.5
通讯作者：
Claire Wyart;S. Cocco;L. Bourdieu;J. Léger;C. Herr;D. Chatenay
中科院分区：
文献类型：
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作者：
Claire Wyart;S. Cocco;L. Bourdieu;J. Léger;C. Herr;D. Chatenay
持续的放电是与工作记忆相关的持续活动所必需的。混响的兴奋和兴奋性突触后电位（EPSP）的时间动态的活动的维持的相对贡献是难以评估的经典制剂。我们使用简化模型的同步兴奋网络，海马autapses和对，研究突触机制的基础上，在低利率的射击。钙成像和细胞贴附记录显示，这些神经元自发地在很宽的频率范围内发出持续数秒的动作电位脉冲。在2周龄的细胞中，中位放电频率较低（11 +/- 8.8 Hz），而在3- 4周龄的细胞中，它降低到非常低的值（2 +/- 1.3 Hz）。在这两种情况下，我们已经表明，最慢的突触组件支持放电。在2周龄autapses，N-甲基-D-天冬氨酸受体（NMDARs）的拮抗剂诱导罕见的孤立的尖峰，表明NMDA组件的EPSP是必不可少的爆发在低频率。在3- 4周龄的神经元中，在没有NMDAR激活的情况下维持非常低的频率放电。然而EGTA-AM或α-甲基-4-羧基苯甘氨酸（MCPG）去除了EPSP的非常缓慢的去极化成分，并阻止了以非常低的速率持续放电。因此，代谢型谷氨酸受体（mGluR）激活的钙敏感性电导是负责一个非常缓慢的突触组件与发射率非常低。此外，我们的观察表明，谷氨酸的异步释放可能也参与了反复爆发。
Sustained firing is necessary for the persistent activity associated with working memory. The relative contributions of the reverberation of excitation and of the temporal dynamics of the excitatory postsynaptic potential (EPSP) to the maintenance of activity are difficult to evaluate in classical preparations. We used simplified models of synchronous excitatory networks, hippocampal autapses and pairs, to study the synaptic mechanisms underlying firing at low rates. Calcium imaging and cell attached recordings showed that these neurons spontaneously fired bursts of action potentials that lasted for seconds over a wide range of frequencies. In 2-wk-old cells, the median firing frequency was low (11 +/- 8.8 Hz), whereas in 3- to 4-wk-old cells, it decreased to a very low value (2 +/- 1.3 Hz). In both cases, we have shown that the slowest synaptic component supported firing. In 2-wk-old autapses, antagonists of N-methyl-d-aspartate receptors (NMDARs) induced rare isolated spikes showing that the NMDA component of the EPSP was essential for bursts at low frequency. In 3- to 4-wk-old neurons, the very low frequency firing was maintained without the NMDAR activation. However EGTA-AM or alpha-methyl-4-carboxyphenylglycine (MCPG) removed the very slow depolarizing component of the EPSP and prevented the sustained firing at very low rate. A metabotropic glutamate receptor (mGluR)-activated calcium sensitive conductance is therefore responsible for a very slow synaptic component associated with firing at very low rate. In addition, our observations suggested that the asynchronous release of glutamate might participate also in the recurring bursting.