생쥐 대장근에서 과분근으로 유발된 내향성 전류의 특성

Abstract

To characterize the hyperpolarization-induced inward currents, membrane currents were measured using a whole-cell patch clamp from isolated colonic myocytes of mouse. With 90 mM K^(+) in bath, hyperpolarization-induced inward currents from -l20 mV to 20 mV with 400 ms duration at a holding potential of -10 mV showed rapid activation, inactivation and inward rectification. The inactivation showed single exponential time course. Reduction of external K^(+) to 60 mM decreased the amplitudes of the currents in whole test voltage range and shifted the reversal potential to more negative potential. The inactivation process and peak currents of hyperpolarization-induced inward currents were not affected by removing external Na^(+). External Ba^(2+) blocked hyperpolarization-induced inward currents by dose-dependent manner and pure Ba^(2+)-sensitive currents showed strong inward rectification. Cs^(+) also suppressed hyperpolarization-induced inward currents. Ba^(2+) and Cs^(+)-induced inhibition of hyperpolarization-induced inward currents was voltage-dependent, and the extent of inhibition increasing with membrane hyperpolarization. These results suggest that inward rectifying K^(+) channels may exist in proximal colonic smooth muscle and may play an important role in regulating membrane potential.