Extracellular pH modulates the voltage-dependent Ca2+ current and low threshold K+ current in hair cells.
Extracellular protons have been shown to modulate voltage-activated ionic channels. It has been proposed that synaptic modulation by exocytosed vesicular protons would be a characteristic feature of ribbon-type synapses. Type-I hair cells have a calyceal afferent junction with a diffusionally restricted synaptic cleft. These led us to study the action of extracellular pH changes on the voltage-activated Ca(2+) and K(+) currents evaluated using a whole-cell patch clamp in isolated cells. The amplitude of the Ca(2+) and the K(+) current were reduced by extracellular acidification, but without significant changes with extracellular alkalization. A shift in the voltage dependence to a more positive membrane potential was achieved at pH < 6.8. Our results shows that the presynaptic K(+) and Ca(2+) currents are modulated by protons, indicating that protons released along with an afferent neurotransmitter would participate as a feedback mechanism in type-I hair cells.
Almanza
Angélica
A
Instituto de Fisiología, Universidad Autónoma de Puebla (BUAP), Apartado Postal 406, Puebla, 72000, Mexico.
Mercado
Francisco
F
Vega
Rosario
R
Soto
Enrique
E
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D006198:Hair Cells, Auditory / Q000166:cytology / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D011522:Protons; D051381:Rats; D020318:Rats, Long-Evans
D015220:Calcium Channels; D015221:Potassium Channels; D011522:Protons; D011188:Potassium; D002118:Calcium