STX - A neurotoxin used in many studies of neurons at the cellular and molecular level. Saxitoxin is believed to be produced by a variety of marine algae. Because algae are at the lower end of the food chain, it is also found in many strains of fish, such as pufferfish, and butter clams (saxidomus giganteus, which is from where the name is derived).

Saxitoxin works by blocking the outside pore of voltage-gated sodium channels.