Response attenuation during coincident afferent excitatory inputs.
Response attenuation during coincident afferent excitatory inputs.
复制标题
同时传入兴奋性输入期间的反应衰减。
DOI：
10.1152/jn.1999.81.6.2945
复制
发表时间：
1999
影响因子：
2.5
通讯作者：
Ariel,M
中科院分区：
文献类型：
--
作者：
Kogo,N;Ariel,M
同时传入兴奋性输入时的反应衰减。 两个单一的兴奋性突触事件的突触总和的线性进行了研究，在全细胞记录视网膜靶神经元的眼睛连接的分离的脑干制备。双极刺激电极根据视觉感受野边界指向视网膜表面的两个不同焦点，诱发成对的单一兴奋性突触后电位（EPSP）。每个视网膜部位的刺激之间的间隔增加0.5-1 ms，以使用指数拟合来量化非线性求和的时间过程。从未观察到反应促进，然而，突触输入的同时到达引起的37对研究中的26个响应衰减。26对中有12对的衰减时间常数与每对的第一个EPSP的衰减阶段的时间常数相似。这表明这12对的衰减可能完全是由于电压依赖性机制，如驱动力的降低或电压敏感通道活性的变化。另一方面，其他14对的衰减时间常数短于第一个EPSP衰减相的时间常数。事实上，衰减时间常数往往更接近每对第一兴奋性突触后电流衰减相的时间常数。这一发现表明，这14对衰减涉及一个分流机制，由于突触通道的开放。这种电导依赖性机制的存在得到了当刺激序列被逆转时对衰减的时间过程的不对称效应的发现的支持。这些结果进行了讨论，在处理一致的兴奋性输入到空间上不同的点，他们的树突树的神经元。
Response attenuation during coincident afferent excitatory inputs. The linearity of the synaptic summation of two unitary excitatory synaptic events was investigated during whole cell recordings from retinal target neurons in an eye-attached isolated brain stem preparation. Pairs of unitary excitatory postsynaptic potentials (EPSPs) were evoked by bipolar stimulation electrodes that were directed to two distinct foci on the retinal surface based on the visual receptive field boundaries. The interval between stimulation of each retinal site was incremented by 0.5–1 ms to quantify the time course of nonlinear summation using an exponential fit. Response facilitation was never observed; however, the coincident arrival of synaptic inputs caused a response attenuation in 26 of the 37 pairs studied. Twelve of the 26 pairs had time constants of their attenuation that were similar to the time constants of the decaying phases of the first EPSPs of each pair. This suggests that the attenuation of these 12 pairs may be entirely due to voltage-dependent mechanisms, such as a reduction in driving force or a change of the activity of voltage-sensitive channels. On the other hand, the 14 other pairs had their time constant of attenuation shorter than the time constants of the decaying phase of the first EPSP. In fact, the attenuation time constants were often closer to the time constants of the decaying phases of the first excitatory postsynaptic currents of each pair. This finding suggests that the attenuation of these 14 pairs involve a shunting mechanism due to the opening of synaptic channels. The presence of this conductance-dependent mechanism is supported by the finding of asymmetric effects on the time course of attenuation when the stimulation sequence was reversed. These results are discussed in terms of the processing by neurons of coincident excitatory inputs onto spatially distinct points of their dendritic trees.