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A neurotoxin is a toxin that acts specifically on nerve cells[1] (neurons), usually by interacting with membrane proteins such as ion channels.
Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue.[2] Bungarotoxin, which is considered a neurotoxin,[3] has its effect at the motor end plate.
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Classification and examples
Venoms
Many of the venoms and 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.
Channel inhibitors
Many neurotoxins act by affecting voltage-dependent ion channels:
| Agent | Channel |
| tetrodotoxin and batrachotoxin | sodium channels |
| maurotoxin, agitoxin, charybdotoxin, margatoxin, slotoxin, scyllatoxin and hefutoxin | potassium channels |
| calciseptine, taicatoxin and calcicludine | calcium channels |
A potent neurotoxin such as batrachotoxin affects the nervous system by causing depolarization of nerve and muscle fibers due to increased sodium ion permeability of the excitable cell membrane.
A very potent neurotoxin is tetrodotoxin. This chemical acts to block sodium channels in neurons, preventing action potentials. This leads to paralysis and eventually death.
Exogenous vs. endogenous
Toxins ingested from the environment are described as exogenous and include gases (such as carbon monoxide), metals (such as mercury), liquids (ethanol) and an endless list of solids. When exogenous toxins are ingested, the effect on neurons is largely dependent on dosage.
Neurotoxicity also occurs from substances produced within the body: endogenous neurotoxins. A prime example of a neurotoxin in the brain is glutamate, which is paradoxically also a primary neurotransmitter.
Nerve agents
A number of artificial neurotoxins, known as nerve agents, have been developed for use as chemical weapons.
References
- ^ "neurotoxin - Definitions from Dictionary.com". dictionary.reference.com. Retrieved on 2008-04-22.
- ^ "Dorlands Medical Dictionary:neurotoxin".
- ^ Kuch U, Molles BE, Omori-Satoh T, Chanhome L, Samejima Y, Mebs D (September 2003). "Identification of alpha-bungarotoxin (A31) as the major postsynaptic neurotoxin, and complete nucleotide identity of a genomic DNA of Bungarus candidus from Java with exons of the Bungarus multicinctus alpha-bungarotoxin (A31) gene". Toxicon 42 (4): 381–90. PMID 14505938.
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- This page was last modified on 20 August 2008, at 04:46.
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