Effects of veratridine and its derivatives on the Na-conducting channels in Helix neurons

Effects of veratrum alkaloids were studied on the Na-channels of the land snail Helix pomatia. It was found that veratridine and its analogues depolarize the membrane due to the increased Na-permeability. The inactivation was shifted right along the voltage axis and the recovery from the inactivation was faster after veratridine treatment. After alkaloid treatment the selectivity of the Na-channel decreased, however, the selectivity sequence was not altered. The activation curve was not shifted. Veratridine derivatives, which appeared to be more effective on insects, had almost no effect on the Na-current.