Abstract: ObjectiveTo evaluate the quantitative and qualitative changes of peripheral-type benzodiazepine recepors (PBRs) in brain mitochodria and in platelet membrane in aging rats. MethodsMale Sprague-Dawley rats were divided into 3- and 24-month groups. All animals were sacrificed by decapitation and the brains were immediately removed. Mitochondrial components from dissected cerebral cortex were isolated. The membrane of platelets from venous blood was prepared by the method of hypotonic hemolysis. The specific binding assay of the radioactive PBRs antagonist ［³H］PK11195 to membrane was performed. Scatchard analysis was performed to estimate the equilibrium dissociation constant (Kd) and the maximal binding site density (Bmax). ResultsA significant increase in ［³H］PK11195 binding activity in the mitochodria from cerebral cortex in 24-month rats was observed compared to that in 3-month rats(P<0-001). Meanwhile, the Scatchard analysis revealed that there was an increase in Bmax, with a significant increase in Kd in 24-month rats. The same change of ［³H］PK11195 binding activity was noted for platelet membrane in 24-month rats(P<0-001).ConclusionThe density of PBRs increases in cortex mitochondria in aging rats, but the binding affinity of PBRs decreases which may be attributable to the progressive pathogenesis of aging in rats. ［³H］ PK11195 binding activity of platelet membrane might reflect the change of PBRs in the brain tissue.

Key words: aging, brain cortex, mitochodria, platelets, peripheral-type benzodiazepine receptors