A neurotoxin is a toxin that acts specifically on nerve cells (neurons), usually by interacting with membrane proteins such as ion channels. Many of the venoms an other toxins that organisms use in defense against vertebrates are neurotoxins. A common effect is paralysis, which sets in very rapidly. The venom of bees, scorpions, pufferfish, spiders and snakes can contain many different toxins. Many neurotoxins act by affecting voltage-dependent ion channels. For example, tetrodotoxin and batrachotoxin affect sodium channels, maurotoxin, agitoxin, charybdotoxin, margatoxin, slotoxin, scyllatoxin and hefutoxin act on potassium channels, and calciseptine, taicatoxin and calcicludine act on calcium channels.