2 components of the high-threshold calcium current possessing different sensitivities to omega-conotoxin in the membrane of pheochromocytoma cells

Blockade of the high-threshold calcium currents by omega-conotoxin (CgTx) was investigated by patch-clamp recordings of whole-cell currents in cultured cells of pheochromocytoma PC12. CgTx (10 mumol/l) preferentially blocked only a steady-state component of the calcium current. Inactivated component was insensitive to CgTx (up to 50 mumol/l concentration). The two component nature of the high-threshold calcium current in pheochromocytoma PC12 cells was suggested.