Alteration of muscarinic receptor subtypes in CA1 field of hippocampus in senile dementia of Alzheimer type: an autoradiographic study.

This investigation confirmed decreases in muscarinic acetylcholine receptor (mAChR) concentration in the hippocampus of patients with senile dementia of Alzheimer-type (SDAT) using a binding assay with homogenate. We performed quantitative in vitro autoradiography of mAChR in the hippocampus obtained at autopsy from non-demented controls and SDAT patients, who had a marked memory disturbance since the early stage. 3H-QNB (1.09nM) and 3H-pirenzepine (18.0nM) were used as ligands to label total mAChR and M1 receptors, respectively. Total mAChR and M1 receptor densities showed a decrease by about 20% and 25%, respectively, in the CA1 area of SDAT cases, when compared with that of normal control cases. No changes were observed in the dentate gyrus, CA3, subiculum or entorhinal cortex. These observations are thought to be partly causative of the marked memory deficits which appeared in these cases.