↵3-a Mean ± S.E.M. (number of neurons). Under control conditions, the rise time of ACh (0.3 mM)-evoked type IA currents ranged from 15 to 27 msec (n = 14). The decay phase of currents recorded from 11 neurons was best fitted by a single-exponential function and the decay-time constant of these currents ranged from 15.2 to 52.1 msec. The decay phase of the currents recorded from three neurons was fitted by a double-exponential function, and the τ_f of these currents, which varied from 14.6 to 22.7 msec, was used in averaging the results.