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THE INFLUENCE OF L‐TRYPTOPHAN AND MONOAMINE OXIDASE INHIBITORS ON CATECHOLAMINE METABOLISM IN RAT BRAIN
Author(s) -
ECCLESTON D.,
NICOLAOU N.
Publication year - 1978
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1978.tb08655.x
Subject(s) - homovanillic acid , normetanephrine , monoamine oxidase , dopamine , 3,4 dihydroxyphenylacetic acid , dopaminergic , chemistry , endocrinology , medicine , catecholamine , monoamine neurotransmitter , tryptophan , serotonin , tryptophan hydroxylase , nialamide , biochemistry , biology , enzyme , amino acid , serotonergic , receptor
1 L‐Tryptophan (100 mg/kg) was administered to rats with or without pretreatment with a monoamine oxidase inhibitor and the concentration of 5‐hydroxyindoleacetic acid, homovanillic acid, dihydroxyphenylacetic acid, 3‐methoxy 4‐hydroxyphenyl glycol, normetanephrine, noradrenaline and dopamine measured in whole brain one hour later. 2 L‐Tryptophan increased the concentration of 5‐hydroxyindoleacetic acid, homovanillic acid, dihydroxyphenylacetic acid, 3‐methoxy 4‐hydroxyphenyl glycol and normetanephrine. The concentration of noradrenaline did not change whilst that of dopamine increased significantly. 3 In animals pretreated chronically with a monoamine oxidase inhibitor, tryptophan increased the concentration of dihydroxyphenylacetic acid and homovanillic acid compared to monoamine oxidase alone. 4 The results suggest either a release of dopamine and noradrenaline by 5‐hydroxytryptamine, with a compensatory increase in their synthesis, or an increase in the firing of dopaminergic and noradrenergic neurones after L‐tryptophan.