Cholinergic poisons, examples

The toxicity of the G and V agents is apparently due to their affect upon the transmission of nerve impulses in the body, due to their ability to react with and inhibit acetylcholinesterase (ChE) enzyme. For example, after a nerve impulse is transmitted across a nerve and muscle junction by acetylcholine, the latter is then rapidly hydrolyzed by ChE. However, in the presence of GB, for example, the hydrolytic sites on the enzyme are irreversibly blocked by phosphorylation, and these sites are no longer available for hydrolysis of the acetylcholine. The resulting buildup of acetylcholine acts to overstimulate the muscle, which eventually goes into spasm. Thus, the typical symptoms of poisoning by a nerve agent are due to its cholinergic activity. 

A racemic mixture of hyoscyamine, the principal tropane alkaloid of Belladonna herb (Atropa belladonna), henbane (Hyoscyamus niger) or stramonium leaf (Datura stramonium) used in medicine when temporary reversible muscarinic blockade is needed, for example, to overcome bradycardia, as an antidote for overdose of cholinergic drugs or cholinesterase poisoning. 

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