Dendritic Membrane Properties of Crayfish Nonspiking Interneurons

用单电极电压钳(SEVC)技术研究了克氏原虾腹神经节中的LDS中间神经元树突膜的生理特性。实验过程中，用蓝光照射填充荧光素的细胞和微电极，在解剖显微镜下原位观察到电极穿透树突的位置。树突膜对细胞内注入的电流在中线粗支和周围支处都有向外的整流。相应地，膜时间常数在去极化时比在超极化时短。直接刺激突触前感觉神经元诱发的复合PSP的时程随着细胞与静息电位去极化程度的增加而缩短，反之亦然。与在…的任何位置观察到的整流膜性质相反更多的枝晶、输入电阻和膜时间常数与电极穿透位置有关。因此，厚桥接部分的输入电阻明显低于外围分支。在桥接部分放置单个细胞内微电极，并将SEVC技术应用于LDS树枝晶。对保持在静息电位的电池施加超极化指令电压(10-50 mV)，观察到与超极化成正比的小的内向泄漏电流。相比之下，电池显示了一个附加的外向电流叠加在外向泄漏电流上。附加电流量取决于去极化的量。这一电流在去极化开始时出现一过性增加，并在大约80-100毫秒内稳定下来。灌流10 mM TEA后，稳定外向电流降低到70-80%，表明它类似于众所周知的延迟整流K电流。暂态早期电流的特性有待进一步研究。较少

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