Jacobson I, Pocock G, Richards C D
Department of Physiology, Royal Free Hospital School of Medicine, London, U.K.
Eur J Pharmacol. 1991 Sep 24;202(3):331-9. doi: 10.1016/0014-2999(91)90275-u.
We have used the whole cell patch clamp technique to investigate the action of pentobarbitone on the nicotinic channels of bovine chromaffin cells. Application of agonists induced an inward current associated with a large increase in current noise. The noise could be fitted by Lorentzian functions with time constants of 17 +/- 2 ms for 10 microM acetylcholine and 10 +/- 1 ms for 10 microM carbachol. The single channel conductance estimated from the current variance was about 25 pS in each case. Pentobarbitone decreased the time constants in a concentration-dependent fashion, but the unit conductances were unaffected. Single channel events were recorded in chromaffin cells held under voltage clamp. Pentobarbitone did not reduce the amplitude of channel openings or the probability of channel opening but reduced the mean channel open time. This reduction was sufficient to account for the decrease in inward current produced by pentobarbitone.
我们运用全细胞膜片钳技术来研究戊巴比妥对牛嗜铬细胞烟碱通道的作用。应用激动剂会诱导出一种内向电流，同时伴随着电流噪声的大幅增加。这种噪声可用洛伦兹函数拟合，对于10微摩尔乙酰胆碱，时间常数为17±2毫秒；对于10微摩尔卡巴胆碱，时间常数为10±1毫秒。根据电流方差估算的单通道电导在每种情况下约为25皮安。戊巴比妥以浓度依赖的方式降低时间常数，但单位电导不受影响。在电压钳制下的嗜铬细胞中记录到了单通道事件。戊巴比妥并未降低通道开放的幅度或通道开放的概率，但缩短了平均通道开放时间。这种缩短足以解释戊巴比妥所产生的内向电流的减少。
