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 a-methyl-p-tyrosine) were measured in male C57BL/6J mice at various ages between 4 and 30 months, the average lifespan of male C57BL/6J mice. No region showed progressive age changes in levels or turnover, or changes before midlife, 8-12 months. 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 aged greater than or equal to 24 months; few changes were statistically significant. CA levels and turnover decreased in some samplings of striatum and median eminence-arcuate nucleus. In contrast, DA levels increased in anterior pituitary and possibly in medial preoptic region. DOPAC levels (measured only in rostral striatum) decreased by 20% at 28 months. These results diverge from the larger, progressive decreases of DA reported in human striatum during aging.