Caffeine rapidly decreases potassium conductance of dissociated outer hair cells of guinea-pig cochlea.
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 (Icaffeine) with decrease of conductance in a dose-dependent manner at a holding potential (VH) of -60 mV. The reversal potential of Icaffeine (Ecaffeine) was close to the K+ equilibrium potential. The Icaffeine was not affected by Ca(2+)-free external solution. The internal perfusion of the Ca2+ chelator BAPTA had no effect on Icaffeine. The Icaffeine was not modulated by the external application of H-8 or staurosporine and by the internal perfusion of GDP-beta S. The amplitude of Icaffeine 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.
Yamamoto
T
T
Department of Physiology, Kyushu University Faculty of Medicine, Fukuoka Japan.
Kakehata
S
S
Yamada
T
T
Saito
T
T
Saito
H
H
Akaike
N
N
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D003051:Cochlea / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004594:Electrophysiology; D019204:GTP-Binding Proteins / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000502:physiology; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects*; D015290:Second Messenger Systems / Q000187:drug effects
D015221:Potassium Channels; D002110:Caffeine; D004533:Egtazic Acid; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium