What is a Neurotoxin?
A toxin is a substance produced by an organism that causes harm when introduced to another organism and usually results in the production of some neutralizing agents (i.e. antitoxins). Neurotoxins are toxins that target the nervous system and disrupt the signaling that allows neurons to communicate effectively. Some neurotoxins achieve this by interrupting the ion channels, while other neurotoxins inhibit the signaling molecules that propagate the action potential from one neuron to the next.
One well-known neurotoxin that disrupts sodium channels, a very important ion channel for the production and propagation of action potentials, is tetrodotoxin (TTX; Fig 1). TTX is known to the public due to its presence in the pufferfish, which, if not prepared correctly, can result in death when consumed (Hwang and Noguchi 2007). Similar to a cork in a wine bottle, TTX stops ions from flowing through the ion channel by acting as a plug (Fig 2). Without the movement of sodium across the neuronal membrane, neurons are not able to properly send signals and communication in the nervous system ceases.
Figure 1. Structure of TTX
Figure 2. Effect of TTX on sodium channel.