HYPERSENSITIVITY OF CORTICAL MUSCARINIC RECEPTORS IN PARKINSONS-DISEASE DEMONSTRATED BY PET

The status of muscarinic receptors (mAChRs) is not clear in Parkinson' s disease (PD). We measured mAChR binding in the brain of eight patien ts with PD and eight, age-matched, healthy controls by positron emissi on tomography (PET) and [C-11]N-methyl-4-piperidyl benzilate ([C-11]NM PB). PD patients were not demented according to DSM III criteria but s howed significant frontal lobe dysfunction in the Modified Wisconsin C ard Sorting Test. A mean K-3 value, which is an index of mAChR binding calculated by a graphical method, was 20% higher in the frontal corte x of PD patients than controls (p<0.05). Hypersensitivity of mAChRs in the frontal cortex of PD patients may be a response to a loss of asce nding cholinergic input to that region, and may relate to frontal lobe dysfunction in PD.