Cerebrospinal fluid cholinesterases--markers for loss of cholinergic basal forebrain neurons?

The present study was conducted to test the hypothesis that cholinergic basal forebrain neurons are a major source of cerebrospinal fluid (CSF) cholinesterases. To address this question enzyme activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in both CSF and parietal cortex were assayed following selective lesion of basal forebrain cholinergic neurons by a single intracerebroventricular application of the cholinergic immunotoxin 192IgG-saporin. Cholinergic immunolesions led to a dramatic decrease in total AChE activity in parietal cortex, which was due to the specific loss of the G4 molecular form while the activity of the G1 form was increased as compared to nonlesioned animals. In contrast, the total enzyme activity of BChE and its molecular forms were not affected by cholinergic lesion in both parietal cortex and CSF. The data suggest, that cholinergic basal forebrain neurons are seemingly not a major source of cholinesterases in the CSF, and do not provide any evidence for using CSF cholinesterases as a diagnostic marker of basal forebrain cholinergic cell loss in humans.