Conductance of the slow inward channel in the rabbit sinoatrial node

Abstract

The elementary conductance of the slow inward current channel in the rabbit sinoatrial node was measured by analysis of the current fluctuations. The preparations were voltage-clamped to −30 mV, where d_∞ and f_∞ of the slow inward current (I_si) intersect. In the presence of Ba, which increases I_si and decreases outward currents, a small steadystate component of I_si could be detected. The fluctuations of the current in 10 mM Ba were smaller due to the block of the outward channels. They were further reduced after the inhibition of I_si by the Ca channel blocker D600. The spectral power density distribution of the current fluctuations originating from I_si could be fitted at frequencies n=10), corresponding to an average open time of the single channel of about 30 msec at −30mV. The single channel conductance was determined to 6.50±3.15 pS (S.D.,n=10).