Neurotoxins

A neurotoxin is a toxinthat acts specifically on nerve cells – neurons– usually by interacting with membrane proteinsand ion channels. Many of the venomsand other toxins that organisms use in defense against vertebratesare neurotoxins. A common effect is paralysis, which sets in extremely rapidly. Examples of neurotoxins include tetrodotoxin, batrachotoxinand components of the venom in bees, scorpions, spidersand snakes.

Toxins taken in from the environmentare described as exogenous and include gases(eg carbon monoxide), metals (such as mercury), liquids(ethanol) and an endless list of solids. When exogenous toxins are taken in, the effect on neurons is largely dependent on dosage. Thus ethanol(alcohol) is inebriating in low doses, only producing mild neurotoxicity. Prolonged exposure to "safe" alcohol levels slowly weakens and kills neurons.

Neurotoxicityalso 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. When the glutamate concentration around a neuron reaches a critical point the neuron kills itself by a process called apoptosis. This whole process is called excitotoxicity, so named because glutamate normally acts as an excitatory neurotransmitter at lower levels.

A potent neurotoxin such as batrachotoxinaffects the nervous system by causing depolarizationof nerve and muscle fibres due to increased sodiumionpermeabilityof the excitable cell membrane.

See also

• neurotoxic
• teratogenesis, many birth defects are essentially caused by neurotoxicity in developing neuronsde:Nervengift

fr:Neurotoxique nl:Neurotoxine

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Neurotoxins Wikipedia article Neurotoxins.