title: Effect of brain monoamine precursors on stress-induced behavioral and neurochemical changes in aged mice.
abstract: Male CF-1 mice aged 22 months showed approximately the same level of motor activity and aggressive behavior as 3-month-old mice under control (no stress) conditions, or 45 min following cold swim stress. Increasing brain catecholamine activity by dietary L-tyrosine treatment had no effect on these two age groups either under control conditions or after stress. In contrast, 30-month-old mice showed lower motor activity under control conditions which was raised significantly by supplementation of the diet with L-tyrosine. However, marked reductions in activity and aggression following stress were observed in the 30-month-old animals and these deficits were not reversed by L-tyrosine treatment prior to stress. Reduction in motor activity was greatest in stressed, 30-month-old mice on L-tyrosine supplemented diets. Compared to 3-month-old mice, the 30-month-old animals had lower brain tyrosine following dietary L-tyrosine treatment, lower brain tryptophan, norepinephrine (NE), dopamine (DA) and DOPAC, but higher HVA, serotonin (5-HT) and 5-HIAA levels. Under both control (no stress) and stress conditions, L-tyrosine pretreatment decreased brain 5-HT in the young animals, but increased 5-HT in the old mice. After stress the 30-month-old animals evidenced only slight increases in levels of blood corticosterone. Brain tyrosine was reduced by stress in the young animals but increased by stress in the old animals. Stress-induced decreases in brain NE and increases in serotonin and 5-HIAA levels were observed in both age groups. These results are consistent with hypotheses concerning age-related alterations in brain monoamine functions and adrenocortical control mechanisms.
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000374:Aggression / Q000187:drug effects*; D000818:Animals; D001679:Biogenic Amines / Q000378:metabolism*; D001921:Brain / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology*; D002364:Caseins / Q000494:pharmacology; D004044:Dietary Proteins / Q000494:pharmacology; D006719:Homovanillic Acid / Q000378:metabolism; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects*; D009638:Norepinephrine / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D013315:Stress, Psychological / Q000503:physiopathology*; D014364:Tryptophan / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D001679:Biogenic Amines; D002364:Caseins; D004044:Dietary Proteins; D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D014443:Tyrosine; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan; D009638:Norepinephrine; D006719:Homovanillic Acid