Neurotoxin
Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity).[3] Neurotoxins are an extensive class of exogenous chemical neurological insults[4] that can adversely affect function in both developing and mature nervous tissue.[5] The term can also be used to classify endogenous compounds, which, when abnormally contacted, can prove neurologically toxic.[4] Though neurotoxins are often neurologically destructive, their ability to specifically target neural components is important in the study of nervous systems.[6] Common examples of neurotoxins include lead,[7] ethanol (drinking alcohol),[8] glutamate,[9] nitric oxide,[10] botulinum toxin (e.g. Botox),[11] tetanus toxin,[12] and tetrodotoxin.[6] Some substances such as nitric oxide and glutamate are in fact essential for proper function of the body and only exert neurotoxic effects at excessive concentrations.
"Neurotoxicology" redirects here. For the scientific journal, see Neurotoxicology (journal).Neurotoxins inhibit neuron control over ion concentrations across the cell membrane,[6] or communication between neurons across a synapse.[13] Local pathology of neurotoxin exposure often includes neuron excitotoxicity or apoptosis[14] but can also include glial cell damage.[15] Macroscopic manifestations of neurotoxin exposure can include widespread central nervous system damage such as intellectual disability,[5] persistent memory impairments,[16] epilepsy, and dementia.[17] Additionally, neurotoxin-mediated peripheral nervous system damage such as neuropathy or myopathy is common. Support has been shown for a number of treatments aimed at attenuating neurotoxin-mediated injury, such as antioxidant[8] and antitoxin[18] administration.
Applications in neuroscience[edit]
Though diverse in chemical properties and functions, neurotoxins share the common property that they act by some mechanism leading to either the disruption or destruction of necessary components within the nervous system. Neurotoxins, however, by their very design can be very useful in the field of neuroscience. As the nervous system in most organisms is both highly complex and necessary for survival, it has naturally become a target for attack by both predators and prey. As venomous organisms often use their neurotoxins to subdue a predator or prey very rapidly, toxins have evolved to become highly specific to their target channels such that the toxin does not readily bind other targets[29] (see Ion Channel toxins). As such, neurotoxins provide an effective means by which certain elements of the nervous system may be accurately and efficiently targeted. An early example of neurotoxin based targeting used radiolabeled tetrodotoxin to assay sodium channels and obtain precise measurements about their concentration along nerve membranes.[29] Likewise through isolation of certain channel activities, neurotoxins have provided the ability to improve the original Hodgkin-Huxley model of the neuron in which it was theorized that single generic sodium and potassium channels could account for most nervous tissue function.[29] From this basic understanding, the use of common compounds such as tetrodotoxin, tetraethylammonium, and bungarotoxins have led to a much deeper understanding of the distinct ways in which individual neurons may behave.