세포 밖 2가 양이온이 과분극에 의해 활성화되는 전류(Ih)에 미치는 영향

Effects of Extacellular Divalent Cations on the Hyperpolarization-activated Currents in Rat Dorsal Root Ganglion Neurons

The hyperpolarization-activated current (Ih) is an inward cation current activated by hyperpolarization of the membrane potential and plays a role as an important modulator of action potential firing frequency in many excitable cells. In the present study we investigated the effects of extracellular divalent cations on Ih in dorsal root ganglion (DRG) neurons using whole-cell voltage clamp technique. Ih was slightly increased in Ca2+-free bath solution. BAPTA-AM did not change the amplitudes of Ih. Amplitudes of Ih were decreased by Ca2+, Mg2+ and Ba2+ dose-dependently and voltage-independently. Inhibition magnitudes of Ih by external divalent cations were partly reversed by the concomitant increase of extracellular K+ concentration. Reversal potential of Ih was significantly shifted by Ba2+ and V1/2 was significantly affected by the changes of extracellular Ca2+ concentrations. These results suggest that Ih is inhibited by extracellular divalent cations (Ca2+, Mg2+ and Ba2+) by interfering ion influxes in cultured rat DRG neurons.