Cholinergic markers,
neuropeptides, and
amines and their metabolites were sampled from identical specimens across 10 neocortical regions in a large sample of
Alzheimer's disease (AD) cases and controls. Levels of
choline acetyltransferase,
acetylcholinesterase,
somatostatin,
corticotropin-releasing factor,
serotonin, and 5-hydroxyindoleacetic
acid were significantly reduced in AD versus controls. After data reduction, the most descriptive neurochemical indices were used to examine the relationship of neurochemical measures and
dementia severity within the AD sample, controlling for age effects.
Dementia severity ratings were based on antemortem assessments (46.9% of AD sample) and postmortem chart review (53.1% of the AD sample).
Choline acetyltransferase activity was highly correlated with clinical
dementia ratings across the neocortex of the AD cases.
Somatostatin and
corticotropin-releasing factor levels were correlated with
dementia severity only when control cases were included in the analyses. None of the
amines, their metabolites, or the
neuropeptides quantified related significantly to
dementia severity in the AD cohort. These data (a) confirm the strong association of
cholinergic deficits with functional impairment in AD and show that this association is independent of age and (b) suggest that of all the neurochemical species quantified, the
cholinergic indices may be unique in their association with
dementia severity.