Caffeine rapidly decreases potassium conductance of dissociated outer hair cells of guinea-pig cochlea

Abstract

The effects of caffeine on the outer hair cells (OHCs) freshly dissociated from guinea-pig cochlea were investigated with the whole-cell patch-clamp technique, in both the conventional and the nystatin perforated patch-clamp configurations under voltage-clamp condition. Application of caffeine (> 1 mM for 10–30 s) induced an inward current ( I caffeine ) with decrease of conductance in a dose-dependent manner at a holding potential ( V H ) of −60 mV. The reversal potential of I caffeine (E caffeine) was close to the K + equilibrium potential. The I caffeine was not affected by Ca 2+-free external solution. The internal perfusion of the Ca 2+ chelator BAPTA had no effect on I caffeine . The I caffeine was not modulated by the external application of H-8 or staurosporine and by the internal perfusion of GDP-βS. The amplitude of I caffeine was the largest at the basal region of OHCs when caffeine was locally applied by the ‘puffer’ method. These results suggest that caffeine induces a decrease in membrane potassium conductance of the OHCs mainly at the basal region without mediating the intracellular signaling pathway.