These effects occurred independent of significant AChE inhibition in cerebellum, blood, trachealis, or isolated airway, suggesting that AChE independent OP-induced airway hyperreactivity is a cross-species phenomenon.
We previously demonstrated that, at concentrations that do not inhibit acetylcholinesterase activity, the OP parathion causes airway hyperreactivity in guinea pigs as a result of functional loss of inhibitory M2 muscarinic receptors on parasympathetic nerves.