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Effect of L‐dopa loading on 5‐HTP decarboxylation in rat brain areas
Author(s) -
Trouvin JH,
Maubrey MC,
Raynal H.,
Jacquot C.
Publication year - 1991
Publication title -
fundamental and clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 73
eISSN - 1472-8206
pISSN - 0767-3981
DOI - 10.1111/j.1472-8206.1991.tb00736.x
Subject(s) - benserazide , serotonin , medicine , chemistry , endocrinology , decarboxylation , dopamine , decarboxylase inhibitor , aromatic l amino acid decarboxylase , 5 hydroxyindoleacetic acid , striatum , hypothalamus , hippocampus , 5 hydroxytryptophan , levodopa , biology , biochemistry , parkinson's disease , receptor , disease , catalysis
Summary— The time course of 5‐hydroxytryptophan (5‐HTP), serotonin (5‐HT), and 5‐hydroxyindoleacetic acid (5‐HIAA) concentrations in four rat brain areas (hypothalamus, hippocampus, striatum and olfactory bulbs) were investigated after treatment with l ‐dopa (125 mg/kg, ip) + benserazide (50 mg/kg, ip). 5‐HTP levels increased as early as 0.5 h, showed maximum accumulation at 1.5 h and returned to control levels within 4 h, while 5‐HT was markedly decreased in all four structures, with a maximum effect at 1.5 h (approximately − 70%) in the four areas. The decrease in 5‐HT was not accompanied by changes in 5‐HIAA levels. In agreement with previous studies, these data demonstrate that l ‐dopa loading interferes with serotonin metabolism in the rat brain. However, in addition to the releasing action of newly‐synthesized dopamine, the accumulation of 5‐HTP and the parallel decrease in 5‐HT indicate a reduction in 5‐HT synthesis. This inhibition could be explained by a competitive effect of l ‐dopa for aromatic aminoacid decarboxylase activity.