Effect of Ca2+ on Cochlear Electrical Activity

The effects of Ca2+-associated chemical agents applied to the cochlea of the guinea pig by perilymphatic perfusion were studied. Ca2+ channel blocker 200 ng/ml-1000 ng/ml affected the function of the stria vascularis. Endocochlear DC potential, EP decreased from +80 mV to 0 mV. Heavy metal, La, Cd, Mn, Co and Ni, which block the Ca2+ chan nel were applied. A concentration, of 10 mM heavy metal decreased EP and CM, but 1 mM had no effect on EP. Bay K 8644, a Ca2+ channel agonist, was also applied to the cochlea. After EP decreased with nifedipine, Bay K 8644 prevented any further decrease. Palmitoyl carnitine, which inhibits the Na/K pump and protein kinase C, decreased EP. H-7, which also inhibits the Na/K pump decreased EP but, the effect was not as pronounced as that of Palmitoyl carnitine. The Na/K pump was important in maintaining the function of the stria vascularis. Ca2+ affects c AMP dependent metabolism. From that perspective, Ca2+ affects the Na/K pump through protein kinase C.