Morphological and biochemical changes in the cholinergic and monoaminergic systems in Alzheimer-type dementia

The integrity of cholinergic and monoaminergic neuronal systems in Alzheimer-type dementia (ATD) was studied using a combination of morphological and biochemical procedures applied to samples from seven ATD brains and ten control brains. On morphological examination, the number of neurons was counted in the nucleus basalis of Meynert (nbM), the locus coeruleus (LC) and the nucleus centralis superior (NCS). Biochemically, the activities of choline acetyltransferase (ChAT) and the concentrations of noradrenaline (NA) and serotonin (5-hydroxytryptamine; 5-HT) were measured in the nbM, LC, NCS, frontal cortex, temporal cortex and occipital cortex. Compared with the controls, the mean number of neurons in the nbM and LC were significantly reduced in the ATD brains. The neuronal loss in the NCS in the ATD brains was not significant. The ChAT activities in all regions from the ATD brains had a tendency to be reduced. Marked reductions in the NA concentrations in the LC and 5-HT concentrations in the temporal and occipital cortices were found in the ATD brains. These findings suggest that various neurotransmitter systems, including cholinergic, noradrenergic and serotonergic systems, are affected in the ATD brains.