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Transmitter‐Like Basal and K + ‐Evoked Release of 3,4‐Dihydroxyphenylalanine from the Striatum in Conscious Rats Studied by Microdialysis
Author(s) -
Nakamura S.,
Goshima Y.,
Yue J. L.,
Misu Y.
Publication year - 1992
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1992.tb09306.x
Subject(s) - microdialysis , dopamine , dihydroxyphenylalanine , striatum , chemistry , benserazide , aromatic l amino acid decarboxylase , dopaminergic , decarboxylase inhibitor , tetrodotoxin , basal ganglia , endocrinology , medicine , neurotransmitter , levodopa , biochemistry , biology , central nervous system , parkinson's disease , receptor , disease
Using microdialysis and HPLC, characteristics of the release of endogenous 3,4‐dihydroxyphenylalanine (DOPA) from striatum in conscious rats were studied in comparison with those of 3,4‐dihydroxyphenylethylamine (dopamine; DA). Purified l ‐aromatic amino acid decarboxylase (AADC) converted a putative peak of DOPA to DA. The retention time of DOPA differed from that of DA and major metabolites of DA and norepinephrine. The DOPA peak of dialysates comigrated with that of authentic DOPA when the pH of the HPLC buffer was modified. The ratio of the basal release of DOPA:DA was 1:2. 3‐Hydroxybenzyl‐hydrazine (NSD‐1015; 100 mg/kg, i.p.), an AADC inhibitor, markedly increased the basal release of DOPA but produced no effect on DA. The basal release of DOPA was markedly decreased by α‐methyl‐ p ‐tyrosine (200 mg/kg, i.p.), substantially tetrodotoxin (1 μ M ) sensitive, and Ca 2+ (removal plus 12.5 m M Mg 2+ addition) dependent. Fifty millimolar K + released DOPA and this release was also Ca 2+ dependent. These characteristics of the basal and evoked release of DOPA were similar to those of DA. The ratio of the evoked release of DOPA:DA was 1:3. These results indicate that DOPA is released under physiological conditions and by K + ‐induced depolarization in a manner similar to that for transmitter DA from striatum in freely moving rats.