Description: At left: Tetrodotoxin inactivates a voltage-gated Na+ channel by binding to site 1 at the extracellular pore opening of the channel. At right: Channelrhodopsin is a light-activated cation channel that conducts H+, Na+, K+, and Ca2+ ions. Therefore, a sodium channel blocker would similarly inhibit the processes involved with this structure. References: Tags: Comments: