general anesthetics modulation of GABAA receptor single-channnel currents

氟烷和异丙酚可增强GABAA系统的活性，而GABAA系统是麻醉机制中最重要的系统之一。为了确定氟烷和丙泊酚是否通过相同的机制增强GABA能反应，我们在原代培养的大鼠皮层神经元上进行了单通道膜片钳实验。每个GABAA受体单通道的开放时间和关闭时间分布由快和慢时间常数之和表示。氟烷和异丙酚均不改变单通道电导。氟烷通过延长开放时间的慢相来增加通道开放的概率，而丙泊酚通过缩短关闭时间的慢相来增加通道开放的概率。因此，尽管氟烷和异丙酚都增加了通道开放概率，从而导致抑制性递质作用期间电荷转移的增加，但它们的作用机制不同。

Halothane and propofol enhance the activity of the GABAA system, which one of the most important systems in the mechanism of anesthesia. To determine whether halothane and propofol enhance GABAergic responses by the same mechanism, we performed single-channel patch-clamp experiments with rat cortical neurons in primary culture. Each of the open-time and closed-time distributions of GABAA receptor single channels was expressed by a sum of fast and slow time constants. Neither halothane nor propofol changed the single-channel conductance. Halothane increased the probability of the channel being open via a prolongation of the slow phase of open time, whereas propofol increased the channel open probability via a shortening of the slow phase of closed time. Thus, although both halothane and propofol augmented the channel open probability, thereby causing an increase in charge transfer during inhibitory transmitter action, they acted by different mechanisms.