Fig. 5. Recovery from ketamine inhibition. In the presence of the nonselective Ca2+channel blocker Cd2+(100 μm), ketamine (100 μm) reversibly inhibited the inward Na+currents (A ). To examine the time course and recovery of the ketamine-evoked inhibition of Na+current depolarizing steps from −100 to −40 mV were applied every 5 s. Ketamine (100 μm) inhibited the peak Na+current from control 85.5 ± 3.6 to 31.3 ± 10.4% of maximum (P < 0.05; n = 7) (B ). Recovery of the Na+currents was nearly complete, to 76.9 ± 7.1% (not statistically different from control, 85.5 ± 3.6%; n = 7) and generally required 8–10 min (B ). Experiments performed with application of vehicle (B ) instead of ketamine indicated there was no time-dependent run-down of the Na+currents in the course of these experiments (control, 85.0 ± 1.3%; after 23 min, 84.6 ± 0.6% of maximum; n = 7).