Sodium and calcium channels in bovine chromaffin cells

Abstract

Voltage-clamp records and single channel properties of Na+ and Ca2+ channels are described. Na+ currents were studied after blockade of Ca2+ channels with 1 mM Ca2+ applied externally. Ca2+ currents were recorded after eliminating Na+ currents with tetrodotoxin. The kinetic properties of Ca2+ channels depend on the nature and concentration of the permeating ion. A simple kinetic scheme is proposed to model the activation pathway of Ca2+ channels. The action potentials of chromaffin cells depend on both Na+ and Ca2+ voltage-dependent permeability systems. Ca2+ ion influx during action potentials induces catecholamine release.