Biophysical and Pharmacological Properties of Large Conductance Ca2+-Activated K+Channels in N1E-115 Cells

The large conductance Ca2+-activated K+channels in differentiated mouse neuroblastoma N1E-115 cells have been studied using patch-clamp single-channel current recording in excised membrane patches. These channels displayed a unitary conductance of 200 pS under symmetrical K+concentrations. Effects of blockade by TEA+, Cs+and Ba2+were different and argued for distinct action mechanisms. The open probability of these channels increased with increasing internal calcium and membrane potential. Maximum sensitivity of these channels ranged over physiological variations of internal calcium at membrane potentials close to zero, suggesting a physiological role for these channels in regulating the membrane potential and Ca2+influx through voltage-dependent Ca2+channels.