BRAIN ACETYLCHOLINESTERASE IN PARKINSON''S DISEASE

The activity of acetylcholinesterase was studied in various autopsy brain samples of nine parkinsonian patients and eight control subjects without extrapyramidal disorders. Putamen and caudate nucleus showed the highest activities of acetylcholinesterase when different brain areas were compared. Acetylcholinesterase values expressed per wet weight or protein were somewhat lower in the extrapyramidal brain regions of parkinsonian patients than in those of controls. When values were calculated per desoxyribonucleic acid (DNA) it was found that extrapyramidal brain regions, especially substantia nigra, showed higher activities in parkinsonian material than in controls. This difference is due to the decrease of DNA which in the substantia nigra mainly reflects the loss of dopaminergic substantia nigra neurons. Furthermore, analyses of dopamine from the same tissue samples showed many times increased acetylcholinesterase-dopamine ratio in parkinsonian brain than in controls. Levodopa alone or combined with a decarboxylase inhibitor did not have any significant effect on the activity of acetylcholinesterase. It is concluded that the cholinergic mechanisms in the extrapyramidal system of parkinsonian brain are not so severely affected as the dopaminergic ones leading to relative and functional cholinergic dominance.