FURTHER OBSERVATIONS ON ELECTRICAL ACTIVITY OF FROG SPINAL GANGLION CELLS IN SODIUM-FREE SOLUTIONS

Abstract

Various quaternary and other ions used in Na-free solution were found to produce prolonged action potentials with a characteristic configuration (i.e., peak, plateau, and slow repolarizing phase) in frog spinal ganglion cell-bodies. The action potential observed in Na-free hydrazinium solution was unique, its configuration closely resembling that observed in normal Ringer. No appreciable correlation could be found between the active membrane potential and the hydrazinium concentration in the external solution; the action potential of cell-bodies soaked in Na-free sucrose solution could be induced by intracellular injection of hydrazinium ion. These results suggest that hydrazinium ion, like other onium ions substituted for Na, is not acting as a charge carrier for the production of action potentials. No appreciable change in excitability was observed in cell-bodies by changing the external Ca concentration, but the electrical activity was eliminated by total withdrawal of Ca ion from the Na-free solution. It is suggested that Ca ion is essential for the excitability but is not acting as charge carrier for the generation of action potentials in Na-free media.