Biochemical changes in the cholinergic system of the ageing brain and in senile dementia

Loss of neurons from the ageing human brain is accompanied by reduction in biochemical markers. Compared with age-matched controls about one third of nerve cell components are lost from the temporal lobe of patients with senile dementia of Alzheimer's type. There is marked loss of choline acetyltransferase activity, especially in the hippocampus. This alteration parallels the intensity of neuropathological damage and relates to prior mental impairment. Smaller changes in other neurotransmitter synthesizing enzymes are generally found.