Actions of a Red Tide Toxin from 'Ptychodiscus brevis' on Single Sodium Channels in Mammalian Neuroblastoma Cells.

摘要

The actions of brevetoxin (PbTX-3) were studied on single, voltage-dependent sodium channels and whole-cell currents from the neuroblastoma x glioma cell line NG108-15. Purified PbTX-3 shifted the activation of sodium channels to membrane potentials negative to normal. PbTX-3 did not alter the single-channel mean open lifetime, suggesting that the toxin does not change the rate of sodium channel inactivation from the open state. There was also no change in single-channel conductance. These results indicate that brevetoxin increases sodium current at rest by shifting the voltage dependence of channel activation and that the resulting depolarization is limited by channel inactivation. (TTL)