A transient outward current in rat sympathetic neurones.

Voltage-clamped rat sympathetic neurones exhibited a transient outward current similar to that previously described in invertebrate neurones and marine egg cells. It had an activation threshold of about -60 mV and displayed both voltage and time-dependent inactivation. In current clamp, this current manifested as a pronounced outward rectification at the onset of electrotonic potentials, increasing the latency to directly-evoked action potentials. The amplitude of the current was dependent on the external K+ concentration and was reduced by 4-aminopyridine.