Muscarinic AChEs are receptors that bind to acetylcholine (ACh) released by the parasympathetic nervous system. Muscarinic receptors are found on cardiac, smooth muscle, and glandular cells. 
When AChE is inhibited or inactivated, ACh accumulates and overstimulates muscarinic receptors, causing a cholinergic crisis. Symptoms of a cholinergic crisis include:
cramps, increased salivation, lacrimation, muscular weakness, paralysis, muscular fasciculation, diarrhea, and blurry vision. 
Muscarinic receptor antagonists can be used to treat AChE poisoning by blocking the binding of ACh to muscarinic receptors. Atropine is a muscarinic antagonist that is often used to treat accidental poisoning from insecticides or nerve gas. Pralidoxime is another antidote that can regenerate AChE. 
Muscarinic receptors can also be stimulated to induce analgesia, or pain relief. Acetyl-L-carnitine increases ACh synthesis and release, which can activate muscarinic receptors and induce analgesia