CHOLINERGIC BINDING-SITES IN RAT-BRAIN - ANALYSIS BY AGE AND COGNITIVE STATUS

Age-related alterations in the density of cholinergic receptor binding and reuptake sites were examined in discrete forebrain regions of beh aviorally tested rats using quantitative autoradiography. Neurochemica l changes associated with chronological age alone were distinguished f rom memory-dependent alterations by correlating density of binding sit es with performance in the Morris water maze task. An initial analysis of tritium quenching indicated no reliable differential quenching in the study population. Modest age-related reductions in selected subtyp es of cholinergic binding sites in basal forebrain, basal ganglia, and thalamus were observed. However, these reductions were not correlated with a spatial memory deficit. In contrast, no significant changes in the analysis by chronological age were detected for the density of [H -3]hemicholinium binding to high affinity choline uptake sites or [H-3 ]pirenzepine binding to M(1) receptors in any brain region but strong correlations were found between behavioral performance of aged rats an d density of these sites in dorsal hippocampal subfield CA3 and dentat e gyrus. These findings indicate the value of combined neurobiological /behavioral assessment.