Figure 5.

MTX- and TiTX-sensitive currents contribute to distinct features of M1 cells' firing type. A, MTX (10 nm)- and TiTX (25 nm)- sensitive currents in M1 PT-projecting cells. Whole-cell current was measured in voltage clamp by stepping to holding potentials between −70 and −30 mV from −80 mV, and the drug-sensitive currents were obtained by subtraction. The MTX-sensitive current includes a transient component that decays rapidly, with no further inactivation, whereas the TiTX-sensitive current decays slowly. B, Population IV curves for the MTX-sensitive current (left, n = 9) and TiTX-sensitive current (right, n = 10). Error bars indicate SEM. C, MTX but not TiTX significantly (p < 0.01) decreases the latency to first spike (top graph), whereas TiTX but not MTX significantly (p < 0.01) attenuates spike-frequency acceleration (bottom graph). Error bars indicate SEM.