Voltage clamp of motoneuron soma.

Concentric microelectrodes were used to voltage-clamp spinal motoneurons. With depolarizing voltage steps, current transients often appear, with some latency and in all-or-none fashion. Voltage-current relations indicate a two- to threefold reduction in resistance between inside and outside when the cell fires. These results suggest that activity does not involve the whole soma-dendritic membrane.