Intra-regional variations in the effect of aging on high affinity choline uptake, choline acetyltransferase and muscarinic cholinergic receptors in rat neostriatum

High affinity sodium-dependent choline uptake (HACU), choline acetyltransferase (ChAT) and quinuclidinyl benzilate binding ([³H]-QNB) are measured in synaptosomal preparations from four areas of the neostriatum of Fischer 344 rats of three different ages (6, 18 and 30 months). There is a marked regional distribution of all three markers, being higher generally in lateral as compared to medial striatal regions. In addition, in the medial neostriatum, all three measures are higher rostally than caudally. HACU is reduced with age in the rostromedial and the caudolateral neostriatum. Small (usually less than 20%) but significant decreases in muscarinic cholinergic receptors occur in all regions of the neostriatum. There are no significant age-associated differences in ChAT activity in any region. The lack of decrease in ChAT is evidence that the reductions in HACU in striatal subregions are not simply the result of a loss of axon terminal integrity. The changes in HACU may reflect altered activity of cholinergic neurons in specific striatal subregions.