title: Effects of dietary tyrosine on L-dopa- and amphetamine-induced changes in locomotor activity and neurochemistry in mice.
abstract: Recent findings suggest that intraperitoneal injections of L-tyrosine at high doses (100 mg/kg) alters amphetamine-induced changes in behavior by restoring amphetamine-induced decreases in whole brain norepinephrine (NE). The present study examined the motor effects of L-dihydroxyphenylalanine (L-dopa) and d-amphetamine sulfate in mice after treatment with a basal casein diet supplemented with L-tyrosine. The basal diet supplemented with 1-4% L-tyrosine, or 1-4% L-phenylalanine, produced no changes in motor activity in otherwise untreated mice. Whereas L-dopa (25-100 mg/kg) following inhibition of extracerebral decarboxylase by Ro 4-4602 (25 mg/kg) slightly decreased activity in diet control (casein) animals, this drug treatment enhanced motor activity in a dose-related fashion when L-tyrosine was added to the diet. Increases in motor activity following low doses of amphetamine (0.75-1.5 mg/kg) in casein control mice were antagonized by dietary L-tyrosine, but a higher dose of d-amphetamine (3 mg/kg) interacted with the addition of L-tyrosine producing an increase in motor activity. Neurochemical changes observed in brain concentrations of tyrosine, dopamine (DA), norepinephrine (NE), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), tryptophan, serotonin (5-HT) and 5-hydroxy-indoleacetic acid (5-HIAA) following drug and diet treatments suggest that 5-HT systems, in addition to catecholamine systems, may be involved in mediating these effects.
authors.affiliation: Department of Psychology, University of Louisville, KY 40292.
authors.forename: J B
authors.initials: JB
authors.lastname: Thurmond
authors.forename: G B
authors.initials: GB
authors.lastname: Freeman
authors.forename: J S
authors.initials: JS
authors.lastname: Soblosky
authors.forename: J R
authors.initials: JR
authors.lastname: Ieni
authors.forename: J W
authors.initials: JW
authors.lastname: Brown
mesh_terms: D000818:Animals; D015306:Biogenic Monoamines / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects*; D003913:Dextroamphetamine / Q000494:pharmacology*; D004032:Diet; D004347:Drug Interactions; D007980:Levodopa / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects*; D010649:Phenylalanine / Q000494:pharmacology; D014443:Tyrosine / Q000494:pharmacology*
chemical_list: D015306:Biogenic Monoamines; D014443:Tyrosine; D007980:Levodopa; D010649:Phenylalanine; D003913:Dextroamphetamine