Fig. 6. Effects of tetrodotoxin (TTX), tetraethylammonium (TEA), and droperidol on repetitive firing in dorsal horn neurons. (Left ) Trains of action potentials elicited in control (control and recovery) and 10 nm tetrodotoxin-containing solutions (left ), control (control and recovery), and 10 mm tetraethylammonium-containing solutions (middle ) as well as control (control and recovery) and 100 μm droperidol-containing solutions (right ). Data are from three different neurons. The trains of action potentials were evoked by injecting depolarizing 0.5-s current pulses into the cells. For all recordings in one column, the strength of the injected current was equal and is given below the lowermost trace.