Dendritic Membrane Properties of Crayfish Nonspiking Interneurons

利用单电极电压钳（SEVC）技术研究了克氏原螯虾腹末神经节中发现的非尖峰中间神经元LDS树突状膜的生理特性。实验时在解剖显微镜下原位观察电极穿透树突的位置，用蓝光照射充满路西法的细胞和微电极。树突膜在中线粗支和外周支均向外整流。因此，去极化过程中的膜时间常数比超极化过程中的膜时间常数短。直接刺激突触前感觉神经元诱发复合PSP的时间过程随着细胞离静息电位去极化程度的增加而缩短，反之亦然。与在任意位置都能观察到整流膜的特性相反，输入电阻和膜时间常数与电极穿透位置有关。因此，在厚桥部分的输入电阻明显低于周边分支。在桥接部分放置单个细胞内微电极，并将SEVC技术应用于LDS树突。在静息电位下施加10-50mV的超极化命令电压时，观察到一个小的内向泄漏电流与超极化成正比。相比之下，电池显示额外的向外电流叠加在向外泄漏电流。附加电流的大小取决于去极化的大小。该电流在去极化开始时呈瞬态增加，并在约80-100msec时趋于稳定。通过灌注10mM TEA，稳定外向电流减少到70-80%，这表明它类似于众所周知的延迟整流器K电流。暂态早期电流的特性有待进一步研究。少

Physiological properties of the dendritic membrane of LDS interneuron, an identified nonspiking interneuron in the terminal abdominal ganglion of the crayfish Procambarus clarkii Girard, have been studied using the single electrode voltage clamp (SEVC) technique. The site of electrode penetration into the dendrite was visualized under the dissecting microscope in situ during experiment by epiilluminating the Lucifer-filled cell and the microelectrode with blue light.The dendritic membrane showed outward rectification to intracellularly injected current both at the thick branch on the midline and at the peripheral branches. Accordingly, the membrane time constant was shorter during depolarization than during hyperpolarization. The time course of compound PSP evoked by direct stimulation of presynaptic sensory neurons became shorter as the cell was more depolarized from the resting potential and vice versa. In contrast to the rectifying membrane property which was observed at any site of … More dendrites, the input resistance and membrane time constant were dependent of electrode penetration sites. Thus, the input resistance was significantly lower at the thick bridge portion than at peripheral branches.A single intracellular microelectrode was placed at the bridge portion and the SEVC technique was applied to LDS dendrites. In response to hypepolarizing command voltage (10-50mV) applied to the cell held at the resting potential, a small inward leakage current was observed in proportion to the hyperpolarization. By contrast, the cell showed an additional outward current superimposed on the outward leakage current. The amount of additional current was dependent of the amount of depolarization. This current showed transient increase at the onset of depolarization and became steady in about 80-100msec. The finding that the steady outward current was reduced to 70-80% by perfusion of 10mM TEA indicates that it resembles the well known delayed rectifier K current. Characteristics of the transient early current are to be further studied. Less