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Picrotoxin, also known as cocculin, is a poisonous crystalline plant compound, first isolated by Pierre Boullay in 1812.〔 (Note: "''Menispermum cocculus''" has been renamed "''Anamirta cocculus''".)〕 The name "''picrotoxin''" is a combination of the Greek words "''picros''" (bitter) and "''toxicon''" (poison).〔 (Note: "''Menispermum cocculus''" has been renamed "''Anamirta cocculus''".)〕 Found primarily in the fruit of the climbing plant ''Anamirta cocculus'', it has a strong physiological action. It acts as a non-competitive channel blocker for the GABAA receptor chloride channels. It is therefore a channel blocker rather than a receptor antagonist. On the other hand, evidence exists that picrotoxin acts as a competitive antagonist, and not as a channel blocker. For example, Newland and Cull-Candy (1992) found that when recording GABA-activated currents in neurons, picrotoxin "did not alter the amplitude of the main conductance state. However, picrotoxin did reduce the frequency of channel openings." They concluded, "Our data are consistent with a mechanism whereby picrotoxin binds preferentially to an agonist bound form of the receptor and stabilizes an agonist-bound shut state. This could, for example, mean that picrotoxin enhances the occurrence of a desensitized state or an allosterically blocked state." As GABA itself is an inhibitory neurotransmitter, infusion of picrotoxin has stimulant and convulsant effects. As such, picrotoxin can be used to counter barbiturate poisoning, that can occur during general anesthesia or during a large intake outside of the hospital. == Chemical structure == Picrotoxin is an equimolar mixture of two compounds, picrotoxinin (C15H16O6) and picrotin (C15H18O7).〔(【引用サイトリンク】 url = http://www.sigmaaldrich.com/catalog/ProductDetail.do?N4=P1675%7CSIGMA&N5=SEARCH_CONCAT_PNO%7CBRAND_KEY&F=SPEC. )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「picrotoxin」の詳細全文を読む スポンサード リンク
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