Selective influence of rat genotype on age-related regional changes in forebrain muscarinic binding

Abstract Muscarinic binding was analyzed in the hippocampus and frontal cerebral cortex of 3 (young) and 24-month-old (aged) inbred Wistar-Kyoto (WKY), Brown-Norway (BN) and Lewis rats, by the specific binding of the antagonist quinuclidinylbenzilate (QNB). While no age-related changes were detected in the hippocampus of all strains, complex changes were found in the cortex. Maximal binding capacity (Bmax) of [ 3 H]QNB was decreased in the cortex of aged WKY rats, remained unchanged in the BN strain and was elevated in Lewis rats. We conclude that regional differences exist in age-related changes in forebrain muscarinic binding which are probably due to differences in the types and connections of cholinoceptive neurons in these regions. The results suggest that it is the rate of these changes which is affected by the rat genotype.