Computer-assisted image analysis to quantify regional and specific receptor ligand binding: Upregulation of [ 3H]QNB and [ 3H]WB4101 binding in denervated hippocampus

Quantitative regional analysis of receptor autoradiographs using the Nikon Magiscan image analysis system permits resolution of regional variations in specific binding in non-homogeneous CNS structures, such as the hippocampus. Cholinergic denervation, produced by fimbrial transections, elicits a 24% increase in atropine-displaceable [ 3H]QNB binding in whole coronal sections of the hippocampal formation, which is greatest in the dorsal subiculum, CA3 and dentate gyrus. This lesion also elicits a 69% increase in lower affinity [ 3H]WB4101 binding which is displaceabte by phentolamine, but not by prazosin. This represents a sum of increases and decreases in binding in several subregions. Taken together, these findings serve to emphasize the need for normalized regional evaluation of subtracted images which have been calibrated, and linearized or transformed, to reveal binding specific to a single site.