Aging: Effects on β-carboline binding in hippocampal subfields

-The CA1 and CA4/area dentata subfields of the hippocampus in young, mature and old rats were examined for age-related change in propyl β-carboline-3-carboxylate (PrCC) binding. ³H-PrCC bound with high affinity (K_d=0.82 nM) to one binding site when ethyl β-carboline-3-carboxylate was used to delineate specific binding. An age dependent change in the maximum number of ³H-PrCC binding sites in the CA1 and CA4/area dentate subfields of the hippocampus were assessed by using a saturating (6 nM) concentration of ³H-PrCC. Although ³H-PrCC specific binding at a saturating concentration (6 nM) was significantly less in both the CA1 and CA4/area dentata subfields of the senescent rat, the magnitude of the decrease was greater in the CA1 region. In addition, the affinity of the ³H-PrCC binding site in both subfields probably did not vary significantly with age. Therefore, the CA1 and CA4/area dentate of the rat hippocampus may not only lose BZ₁ receptors or the BZ₁ receptors conformation with age, but the severity of receptor or receptor conformation loss varies with the subfield.