Two modes of activity of nicotinic acetylcholine receptor channels in sympathetic neurons

Spectral analysis of acetylcholine (ACh) noise was performed in voltage-clamped neurons of the isolated rabbit superior cervical ganglion at 34–37°C and at membrane potential −80 mV. Two modes of activity were found in the ionic channels of nicotinic ACh receptors, with mean channel life-times of τ_f = 1.1 ± 0.1 ms for fast-operating channels and τ_s = 5.6 ± 0.6 ms for slow-operating channels. Excitatory postsynaptic current (EPSC) decays exponentially with a time constant which is very close to τ_s, indicating that the slow-operating channel activity determines the duration of EPSC. The mean value of conductance of single nicotinic ACh-receptor channel is 36 ± 3 pS.