An N-shaped current-voltage relationship in rat sympathetic neurones

Neurones in the rat isolated superior cervical ganglion were voltage clamped using 2 independent microelectrodes. From a holding potential of -40mV, depolarizing voltage commands to potentials more positive than -20mV elicited outward currents. The current-voltage relationship displayed an N-characteristic with a minimum at +80 to +100mV. Replacement of the external Ca++ ions with Mn++ reversibly abolished a part of the total outward current. The results indicate that rat sympathetic neurones exhibit two potassium currents, a delayed rectifier current and a Ca++-dependent potassium current.