A subcortico-cortical cholinergic system is affected in Parkinson's disease.

CAT activity was decreased in the frontal cortex and the substantia innominata of parkinsonian subjects, post-mortem. The decrease was greater in the frontal cortex of parkinsonians with dementia. The density of muscarinic cholinergic receptors increased in the cortex. This increase was inversely correlated with tremor. The effects on these parameters of both neuronal degeneration and anticholinergic therapy are discussed.