Sensitivity of high-conductance potassium channels in synaptosomal membranes from the rat brain to intracellular pH.

High-conductance potassium channels have been studied in inside-out patches excised from proteoliposomes reconstituted from giant liposomes and rat brain synaptosomes. Acid pH in the medium reduced single channel current amplitude and increased the mean open probability and the frequency of channel opening. This was accompanied by a shortening of the open time constant at positive potential and by shortening of the longer closed time constant. The decrease of channel amplitude, the increase of the open probability and the decrease in the longer closed time constant can be explained by neutralization of negative charges of the membrane and by a decrease in the surface membrane potential which mimics membrane depolarization. The shortening of the mean open time is apparently due to a channel blockade by protons.