MEASUREMENT OF INTRACELLULAR FREE CA2-PIG SPIRAL GANGLION-CELLS( CONCENTRATION IN GUINEA)

INTRACELLULAR free Ca2+ concentration ([Ca2+](i)) in spiral ganglion c ells (SGC) of guinea pig was measured using the fura-2 fluorescence me thod. Application of high-K+ external solution increased [Ca2+](i). [C a2+](i) elevation was suppressed by either depletion of external Ca2or application of the dihydropyridine Ca2+ channel antagonist, nicardi pine. One of the putative hair cell afferent nerve neurotransmitters, L-glutamate (Glu), induced [Ca2+](i) elevation in SGC. Pharmacological studies suggested that the Glu receptor may be a non-NMDA subtype. Gl u-induced response was suppressed by either depletion of external Ca2 or application of nicardipine, indicating that Glu-induced [Ca2+](i) elevation is mainly carried out by the voltage-dependent Ca2+ channel in SGC.