Distribution of m1 muscarinic acetylcholine receptors in the hippocampus of patients with Alzheimer's disease and dementia with Lewy bodies-an immunohistochemical study.

Of the five subtypes (m1-m5) of muscarinic acetylcholine receptors (mAChR), the m1 subtype is the most abundant in the human cerebral cortex and hippocampus. Impairment of the muscarinic cholinergic system in the brain may cause cognitive dysfunction in patients with Alzheimer's disease (AD), and choline esterase inhibitors (ChE-I) are used to improve cognitive dysfunction. Severe impairment of the cholinergic system has also been reported in the brains of subjects with dementia with Lewy bodies (DLB). There have been a few reports about the distribution of mAChR subtypes in the human brain. In the present study, we investigated the distribution of m1 mAChR in the human hippocampus using an antibody against the m1 subtype. In the control brains, m1 immunoreactivity was observed in the apical dendrites and cell bodies of granular neurons of the dentate gyrus and pyramidal neurons of CA1-3 and the subiculum. The dendrites and the cell bodies of the pyramidal neurons in layers III and V of the parahippocampal cortex and other temporal cortices were also positive for m1 immunoreactivity. This m1 immunoreactivity was markedly reduced in AD and DLB brains.