Fig. 3. Depression of mean peak Na⁺currents in cardiac parasympathetic neurons. Cesium was included in the patch pipette to block voltage-gated K⁺currents and isolate the Na⁺current for study. Depolarizations to potentials more positive than −60 mV activated voltage-gated Na⁺currents (A ). To examine whether ketamine altered these Na⁺currents, current–voltage relations were constructed during control and at each ketamine concentration (B ). Compared with control currents, ketamine significantly inhibited the voltage-gated Na⁺currents at potentials from −50 to +10 mV and all concentrations tested (10 μm–1 mm; n = 7;B ). Currents were normalized to the value of the peak mean current in control, which occurred at −50 mV. *P < 0.05 versus  control. **P < 0.01 versus  control.