Prolonged acetylcholine-induced vasodilatation in the peripheral microcirculation of patients with chronic fatigue syndrome
When we stimulate blood vessels with acetylcholine, as described above, its effects usually fade fairly quickly and blood flow returns to normal. This is because an enzyme called cholinesterase is continually removing acetylcholine from the vessel wall and limiting its activity.
However, in further experiments it was found that the blood flow response to acetylcholine in people with ME/CFS, as well as being abnormally high, was also abnormally prolonged (by about 10 minutes). This suggests that in this illness, there is either a reduced amount of cholinesterase available to remove the acetylcholine, or else it is not as effective.
These findings are further evidence of a disturbance to acetylcholine in ME/CFS, and suggest that a cholinesterase abnormality is involved, although this needs to be confirmed by measuring the enzyme directly.