title: Extracellular pH modulates the voltage-dependent Ca2+ current and low threshold K+ current in hair cells.
abstract: 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.
authors.affiliation: Instituto de Fisiología, Universidad Autónoma de Puebla (BUAP), Apartado Postal 406, Puebla, 72000, Mexico.
authors.forename: Angélica
authors.initials: A
authors.lastname: Almanza
authors.forename: Francisco
authors.initials: F
authors.lastname: Mercado
authors.forename: Rosario
authors.initials: R
authors.lastname: Vega
authors.forename: Enrique
authors.initials: E
authors.lastname: Soto
mesh_terms: 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
chemical_list: D015220:Calcium Channels; D015221:Potassium Channels; D011522:Protons; D011188:Potassium; D002118:Calcium