Temperature Enhances Activation and Inactivation Kinetics of Potassium Currents in Inner Hair Cells Isolated from Guinea-Pig Cochlea
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Objectives. Until recently, most patch-clamp recordings in inner hair cells (IHCs) have been performed at room temperature. The results acquired at room temperature should be corrected if they are to be related to in vivo findings. However,the temperature dependency to ion channels in IHCs is unknown. The aim of this study was to investigate the effect of temperature on the potassium currents in IHCs. Methods. IHCs were isolated from a mature guinea-pig cochlea and potassium currents were recorded at room temperature (around 25°C) and physiological temperatures (35°C-37°C). Results. IHCs showed outwardly rectifying currents in response to depolarizing voltage pulses, with only a slight inward current when hyperpolarized. The amplitude of both outward and inward currents demonstrated no temperature dependency,however, activation and inactivation rates were faster at 36ºC than at room temperature. Half-time for activation was shorter at 36°C than at room temperature at membrane potentials of -10, +10, +20, +30, and +40 mV. Q10 for the activation rate was 1.83. The inactivation time constant in outward tetraethylammonium-sensitive potassium currents was much smaller at 36°C than at room temperature between the membrane potentials of -20 and +60mV. Q10 for the inactivation time constant was 3.19. Conclusion. The results of this study suggest that the amplitude of potassium currents in IHCs showed no temperature dependence either in outward or inward-going currents, however, activation and inactivation accelerated at physiological temperatures.
Abstract
Objectives. Until recently, most patch-clamp recordings in inner hair cells (IHCs) have been performed at room temperature. The results acquired at room temperature should be corrected if they are to be related to in vivo findings. However,the temperature dependency to ion channels in IHCs is unknown. The aim of this study was to investigate the effect of temperature on the potassium currents in IHCs. Methods. IHCs were isolated from a mature guinea-pig cochlea and potassium currents were recorded at room temperature (around 25°C) and physiological temperatures (35°C-37°C). Results. IHCs showed outwardly rectifying currents in response to depolarizing voltage pulses, with only a slight inward current when hyperpolarized. The amplitude of both outward and inward currents demonstrated no temperature dependency,however, activation and inactivation rates were faster at 36ºC than at room temperature. Half-time for activation was shorter at 36°C than at room temperature at membrane potentials of -10, +10, +20, +30, and +40 mV. Q10 for the activation rate was 1.83. The inactivation time constant in outward tetraethylammonium-sensitive potassium currents was much smaller at 36°C than at room temperature between the membrane potentials of -20 and +60mV. Q10 for the inactivation time constant was 3.19. Conclusion. The results of this study suggest that the amplitude of potassium currents in IHCs showed no temperature dependence either in outward or inward-going currents, however, activation and inactivation accelerated at physiological temperatures.
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