Recombinant acetylcholinesterase has behavioural effects in the rat substantia nigra not attributable to its enzymatic activity.

An unexplained action of acetylcholinesterase (AChE) has previously been demonstrated on motor behaviour in the substantia nigra: a single infusion of the protein induced long-term circling behaviour, reflecting sustained increased activity of the nigro-striatal pathway. In this study, a highly purified form of AChE was infused and the long-term behavioural effects were still observed. In addition, recombinant human AChE produced a similar response, suggesting that AChE itself, and not a contaminant, was responsible for these behavioural actions. Butyrylcholinesterase, which also hydrolyses acetylcholine, was without effect. Hence AChE is not exerting these actions by potentiating the neurotransmitter acetylcholine, but via some cholinergic-independent mechanism.