Dudel J, Franke C
Pflugers Arch. 1987 Mar;408(3):307-14. doi: 10.1007/BF02181474.
Single, glutamate activated ionic channel currents were recorded from crayfish muscle in the cell attached mode. Different concentrations of glutamate were present in the patch clamp pipette. Bursts of openings were observed with a concentration dependent number of short gaps per burst. Also the mean burst length was concentration dependent and varied between 0.3 ms (100 microM) and 1.3 ms (20 mM). Even with the highest concentrations of glutamate the channel activations were well separated and the beginning and the end of a burst could be defined. The distributions of open times and of burst lengths could be fitted well with a single exponential component for all studied concentrations of glutamate. The distributions of closed times were composed of two or three exponential components (with possibly more than one channel contributing). The mean burst length was compared with the time constants of decay of synaptic currents (0.8-3.0 ms at 19 degrees C) which were measured either with the same pipette as the single channel currents or with a macro patch technique. An estimation of the glutamate concentration at the receptors during synaptic transmission gave values in the millimolar range. The most simple model of glutamate-receptor interaction contains two binding sites for glutamate but no singly liganded open states. Rate constants were estimated for this model.
采用细胞贴附模式记录小龙虾肌肉中单个谷氨酸激活的离子通道电流。膜片钳微管中含有不同浓度的谷氨酸。观察到通道开放呈簇状，每簇的短暂间隙数量呈浓度依赖性。平均爆发长度也呈浓度依赖性，在0.3毫秒（100微摩尔）至1.3毫秒（20毫摩尔）之间变化。即使在最高浓度的谷氨酸作用下，通道激活也能很好地分开，并且可以确定爆发的开始和结束。对于所有研究的谷氨酸浓度，开放时间和爆发长度的分布都可以用单一指数成分很好地拟合。关闭时间的分布由两个或三个指数成分组成（可能有多个通道参与）。将平均爆发长度与突触电流的衰减时间常数（19℃时为0.8 - 3.0毫秒）进行比较，突触电流是用与单通道电流相同的微管或宏观膜片技术测量的。对突触传递过程中受体处谷氨酸浓度的估计得出的值在毫摩尔范围内。最简单的谷氨酸 - 受体相互作用模型包含两个谷氨酸结合位点，但没有单配体开放状态。为此模型估计了速率常数。
