Depolarization of human neuroblastoma cells as a result of muscarinic receptor‐induced rise in cytosolic Ca2+

Abstract

The role of intracellular free Ca²⁺ in muscarinic-receptor linked depolarization of SH-SY5Y neuroblastoma cells has been determined by using the bisoxonol membrane potential probe DiBaC₄−(3) and intracellular Ca²⁺ indicator fura-2-respectively. Carbachol and the Ca²⁺ ionophore, ionomycin, at concentrations which caused similar rises in intracellular Ca²⁺ increased the bisoxonol fluorescence (depolarization) to the same extent. The membrane potential responses, but not the changes in intracellular Ca²⁺, were dependent on extracellular Na⁺. Ionomycin depletion of intracellular Ca²⁺ with EGTA and ionomycin or loading the cells with a Ca²⁺ buffer, BAPTA, reduced the carbachol-induced depolarization. The results suggest that a rise in intracellular Ca²⁺ may cause depolarization through an increase in the Na⁺ permeability.