Cull-Candy S G
Proc R Soc Lond B Biol Sci. 1984 May 22;221(1224):375-83. doi: 10.1098/rspb.1984.0039.
Inhibitory junctional currents (i.j.c.s) have been examined in locust muscle fibres to give properties of GABA-channels activated by the neurally released transmitter. A nerve-muscle preparation is described which has proved suitable for voltage-clamp analysis of inhibitory transmission. I.j.c.s were recorded from fibres in which excitatory synapses had been desensitized with glutamate, to abolish excitatory junctional currents. This procedure had no apparent effect on inhibitory channel properties. The time constant of decay of the i.j.c. was 7.7 +/- 0.3 ms, slightly exceeding the time constant of the membrane noise induced by externally applied GABA. Peak i.j.c. conductance decreased with hyperpolarization. I.j.c.s showed measurable fluctuations permitting an estimate of the mean size of the quantal events composing the i.j.c. Their mean size coincided with the spontaneously occurring miniature inhibitory junctional currents that could be directly recorded in some fibres. The inhibitory nerve-impulse released an average of 35 transmitter packets at sites distributed along the muscle fibre length. Since each m.i.j.c. produced a current of about 0.6 nA (at Vm = -80 mV, ECl = -40 mV) the single quantum of inhibitory transmitter opens 600-1000 postsynaptic chloride channels. This is roughly three to four times the number of channels opened by the excitatory transmitter packet at glutamate synapses in the same fibres.
已对蝗虫肌肉纤维中的抑制性连接电流（i.j.c.s）进行了检测，以了解由神经释放的递质激活的GABA通道的特性。本文描述了一种神经 - 肌肉标本，该标本已被证明适用于抑制性传递的电压钳分析。i.j.c.s是从用谷氨酸使兴奋性突触脱敏以消除兴奋性连接电流的纤维中记录的。此操作对抑制性通道特性无明显影响。i.j.c.的衰减时间常数为7.7±0.3毫秒，略超过外部施加GABA引起的膜噪声的时间常数。i.j.c.的峰值电导随超极化而降低。i.j.c.s显示出可测量的波动，从而可以估计构成i.j.c.的量子事件的平均大小。它们的平均大小与某些纤维中可直接记录的自发产生的微小抑制性连接电流一致。抑制性神经冲动在沿肌肉纤维长度分布的部位平均释放35个递质小包。由于每个微小抑制性连接电流（m.i.j.c.）产生约0.6 nA的电流（在Vm = -80 mV，ECl = -40 mV时），单个抑制性递质量子打开600 - 1000个突触后氯化物通道。这大约是同一纤维中谷氨酸突触处兴奋性递质小包打开的通道数量的三到四倍。
