Effects of ketamine on voltage-dependent calcium currents and membrane potentials in single bullfrog atrial cells
Purpose. This study was undertaken to assess the effect of ketamine on L-type calcium channel current (ICa) and membrane action potential in the bullfrog single atrial myocyte.
Methods. Bullfrog single atrial myocytes were prepared by enzymatic dispersion. Whole-cell voltage-clamp technique and current clamp technique were used to monitor ICa, membrane resting potential, and action potential.
Results. Ketamine (10−5–10−3 M) showed dose-dependent inhibition of ICa in a reversible manner. The 50% inhibitory concentration (IC50) of ketamine on ICa was estimated to be 0.92 × 10−5 M. Use-dependent block of ICa was not observed. The resting membrane potential was depolarized at a high concentration (10−4 M) of ketamine. Reduction of the plateau phase and prolonged duration of the action potential were observed in the presence of a high concentration of ketamine (10−4 M).
Conclusion. Ketamine has an inhibitory effect on ICa in the bullfrog single atrial myocyte, and a high dose (10−4 M) of ketamine prolonges the duration of the action potential. The mechanism of inhibition of ICa seems to be a direct effect on the L-type calcium channel, not like an open channel blocker.
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