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Differential Calcium Dependence Between the Release of Endogenous Dopamine and Noradrenaline from Rat Brain Synaptosomes
Author(s) -
Okada Mitsuko,
Mine Kazunori,
Fujiwara Michihiro
Publication year - 1990
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.1471-4159.1990.tb04896.x
Subject(s) - dopamine , endogeny , calcium , synaptosome , chemistry , neuroscience , biophysics , medicine , biology , biochemistry , organic chemistry
The characteristics of the release of endogenous dopamine and noradrenaline from rat brain synaptosomes were studied using HPLC with an electrochemical detector. The spontaneous release of dopamine and noradrenaline was inhibited by ∼50–60% in a Ca 2+ ‐free medium or a 100 μ M La 3+ ‐containing medium. Also, the high‐K + (30 m M )‐evoked release of dopamine and noradrenaline was inhibited by ∼50–60% in a Ca 2+ ‐free medium or a 100 μ M La 3+ ‐containing medium. From these results, the ratio of the Ca 2+ ‐dependent component to the total release of noradrenaline seemed to be similar to that of dopamine. On the other hand, 20 μ M La 3+ or 1 μ M diltiazem inhibited both the spontaneous and 30 m M K + ‐evoked release of dopamine by ∼50–60% but inhibited neither the spontaneous nor the 30 m M K + ‐evoked release of noradrenaline. The K + ‐evoked rise in intrasynaptosomal Ca 2+ concentration was mostly blocked in Ca 2+ ‐free medium or 100 μ M La 3+ ‐containing medium but was only partially blocked by 20 μ M La 3+ or 1 μ M diltiazem. These data indicate alternative possibilities in that the Ca 2+ ‐dependent release of noradrenaline might be less sensitive to a change of intracellular Ca 2+ concentration than that of dopamine and that the calcium channels directly involved in the noradrenaline release may be more resistant to diltiazem and La 3+ than those involved in the dopamine release.