CATECHOLAMINE LEVELS AND TURNOVER DURING AGING IN BRAIN-REGIONS OF MALE C57BL-6J MICE

A radioenzymatic assay is described for measuring brain catecholamines (CA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the same tissue extract. The [3H]-methylated products are differentially extracted and then acetylated by acetic anhydride, followed by thin layer chromatography in non-basic solvents. Routine sensitivity is 3-5 pg per sample. This assay gave CA levels in brain regions which generally agreed with previous reports. CA levels/mg protein and turnover (after injection of .alpha.-methyl-p-tyrosine) were measured in male C57BL/6J mice at various ages between 4-30 mo., the average lifespan of male C57BL/6J mice. No region showed progressive age changes in levels or turnover, or changes before midlife, 8-12 mo. Brain regions with no evidence of age changes include globus pallidus, zona incerta, substantia nigra, cerebellum and olfactory bulbs. Small changes (10-25%) were detected in only some regions of mice .gtoreq. 24 mo.; few changes were statistically significant. CA levels and turnover decreased in some samplings of striatum and median eminence-arcuate nucleus. DA levels increased in anterior pituitary and possibly in medial preoptic region. DOPAC levels (measured only in rostral striatum) decreased by 20% at 28 mo. The results diverge from the larger, progressive decreases of DA reported in human striatum during aging.