Depolarizing responses to capsaicin in a subpopulation of rat dorsal root ganglion cells.

Microelectrode recordings from the somata of rat dorsal root ganglion (DRG) cells were used to correlate their electrophysiological characteristics with sensitivity to locally applied capsaicin. Of the 80 cells tested, 17 responded to capsaicin by a rapid depolarization. These cells had low axonal conduction velocities (less than 1.4 m/s) and long duration action potentials, characteristic of C-cells. Some C-cells did not respond to capsaicin, and no A-cells, which had high conduction velocities and brief action potentials, did so. The effect of capsaicin on the current-voltage curve of C-cells suggested that it produced a conductance increase as well as a change in delayed rectification.