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Responses of rat substantia nigra compacta neurones to L‐DOPA
Author(s) -
Mercuri Nicola B.,
Calabresi Paolo,
Bernardi Giorgio
Publication year - 1990
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.1476-5381.1990.tb15792.x
Subject(s) - substantia nigra , dopamine , sulpiride , pars compacta , aromatic l amino acid decarboxylase , electrophysiology , chemistry , hyperpolarization (physics) , membrane potential , tetrodotoxin , sch 23390 , endocrinology , apomorphine , medicine , pharmacology , neuroscience , dopaminergic , biology , biochemistry , stereochemistry , nuclear magnetic resonance spectroscopy
1 The electrophysiological actions of l ‐DOPA were studied on substantia nigra dopamine‐containing neurones by use of intracellular recordings, current and voltage clamp, in vitro . 2 l ‐DOPA (3–300 μ m ), applied by superfusion, decreased the spontaneous firing activity of the neurones, hyperpolarized the membrane potential and produced an outward current. 3 These effects of l ‐DOPA were graded and were antagonized by sulpiride, a D 2 ‐receptor antagonist. 4 The l ‐DOPA activated membrane hyperpolarization persisted in slices exposed to tetrodotoxin while it was markedly reduced or abolished in solutions with no calcium plus cobalt (2 m m ). 5 In slices treated with carbidopa, an inhibitor of the aromatic amino acid decarboxylase enzyme, the actions of l ‐DOPA were greatly reduced. 6 We propose that l ‐DOPA inhibits the firing of substantia nigra zona compacta neurones by being converted to dopamine which is then released by these cells.