Block by Cs of K currenti K1 and of carbachol induced K currenti Cch in frog atrium

Abstract

1. In frog atrium, Cs ions block both the inward rectifieri _K1 and the carbachol induced K currenti _Cch. 2. Bothi _K1 andi _Cch display a high affinity for Cs with a K_0.5 of 4×10⁻⁵ M fori _k1 and of 8×10⁻⁵ M fori _Cch atV=−50 mV. 3. Block of bothi _K1 andi _Cch is strongly voltage dependent. When fitted by the block model of Woodhull (1973), δ is >1 for the two currents. 4. From these similarities, action of Cch on frog atrium K permeability could be interpreted as a modification ofi _K1.