Substance P-like immunoreactivity, choline acetyltransferase activity and cholinergic muscarinic receptors in Alzheimer's disease and multi-infarct dementia.

Substance P-like immunoreactivity, choline acetyltransferase (ChAT) activity and muscarinic cholinergic receptors were measured in brains from 9 individuals with senile dementia of the Alzheimer type (AD), 4 individuals with multi-infarct dementia (MID), 6 individuals with mixed type of dementia (AD/MID) and 9 controls. The ChAT activity was markedly reduced (50-60%) in the hippocampus of all demented brains. The number of muscarinic cholinergic receptors was reduced only in the MID and AD/MID brains. No significant difference in substance P-like immunoreactivity was measured in 4 regions of AD brains in comparison to controls. In the combined MID plus AD/MID groups a significant reduction in substance P-like immunoreactivity (-35%) was measured in the hippocampus while no change was found in the frontal cortex, amygdala and caudate nucleus. The findings support the assumption of differences in selectivity of damage between AD and AD/MID, MID.