Effect of catecholamine precursors on stress-induced changes in motor activity, exploration, and brain monoamines in young and aged mice

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In 2 experiments, 24-mo-old male CF-1 mice showed the same level of motor activity and exploratory behavior as 3-mo-old mice under control (no stress) conditions or 45 min following cold-swim stress. Within 90 min after stress exposure, motor activity level in both age groups returned to control values. 30-mo-old Ss showed lower motor activity under control conditions and marked reductions in activity and exploration following stress, which recovered to only half of the control value 90 min after stress. These deficits in the 30-mo-olds were not reversed by levotyrosine or levodopa treatment prior to stress. Levotyrosine supplement did not affect any of the behavioral measures, despite having pronounced effects on brain tyrosine levels. Compared with 3-mo-old Ss, the 30-mo-olds had lower brain tyrosine following dietary levotyrosine treatment, lower norepinephrine (NE), dopamine, and dihydroxyphenylacetic acid, but higher homovanillic acid levels; after stress, they evidenced only slight increases in levels of blood corticosterone. Stress-induced decreases in brain NE and increases in serotonin and 5-hydroxyindolacetic acid levels were observed in both age groups. (48 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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