Effect of ketamine on transient outward potassium current of isolated human atrial myocytes

The effects of ketamine on transient outward potassium current (I_to) of isolated human atrial myocytes were investigated to understand the mechanism of part of its effects by whole-cell patch-clamp.  Atrial myocytes were enzymatically isolated from specimens of human atrial appendage obtained from patients under going cardiac valve displacing.  I_to is recorded in voltage-clamp modes using the patch-clamp technique at room temperature.  Currents signals were recorded by an Axopatch 200B amplifier with the Digidata 1322A-pClamp 9.0 data acquisition system.  Ketamine decreased I_to of human atrial myocytes in a dose-dependent manner.  The current-voltage curve was significantly lowered, 30, 100, 300, and 1 000 µmol·L⁻¹ ketamine decreased respectively I_to current density about (13.62 ± 0.04)%, (38.92 ± 0.05)%, (72.24 ± 0.10)% and (83.84 ± 0.05)% at the potential of 50 mV, with an IC₅₀ of 121 µmol·L⁻¹.  The I_to activation curve, inactivation curve and the recovery curve were not altered by ketamine. So, ketamine concentration-dependently decreased I_to of human atrial myocytes.