Modification of single sodium channels in neuroblastoma cells by chloramine-T

We have studied the behaviour of single sodium channels in cell-attached patches in neuroblastoma cell line N1E 115 at 8-15 degrees C modified by chloramine-T (CT). Application of the agent to the external surface of the membrane cause different effects: CT binds to the membrane and cause irreversible effects leading to a decrease of open channel lifetime at 10 or 20 mV relative potentials without affecting the amplitude of single channel current. Channels modified by CT show a tendency to occur in burst (they can open and close several times during depolarization). Therefore, the slower decay of the average current must be explained by the flickering behaviour of the modified channels. We also examined the effect of CT on the relationship between open time of the channels and membrane potential. On the other hand, a small decrease in the mean delay time as a function of membrane voltages was observed which probably is related to the three state model of inactivation. Our results suggest that CT modifies sodium channel inactivation.