Nerve agents anticholinesterase action

Clinically, the most important effects of OP nerve agents are anticholinesterase actions. However, it should not be forgotten that OPs bind to a variety of enzymes, including esterases other than acetylcholinesterase, e.g. carboxylesterase, (long-chain fatty acid hydrolase), serine... 

Anticholinesterase A substance that blocks the action of chohnesterase (acetylcholinesterase), such as nerve agents. 

Of the various mechanisms of action ascribed to nerve CW agents in various in vitro model systems, most appear to be active at concentrations where significant inhibition of AChE would be expected to occur. These conditions are unlikely to be seen in the absence of recognizable cholinergic toxicity and hence would not be classified as a low-dose effect. The one effect that seems to occur at a sufficiently low concentration of organophosphorus anticholinesterase to be considered a low-dose phenomenon is the slow allosteric modulation of muscarinic receptors regulating presynaptic release of other neurotransmitters. The observation that this allosteric modulation requires several hours to develop suggests that this mechanism would most likely be applicable to a subacute or subchronic exposure rather than one seen after a brief, acute dose. 

---