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Electrically‐evoked dopamine and acetylcholine release from rat striatal slices perfused without magnesium: regulation by glutamate acting on NMDA receptors
Author(s) -
Jin Shaoyu,
Fredholm Bertil B
Publication year - 1997
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 - 10.1038/sj.bjp.0701267
Subject(s) - kynurenic acid , chemistry , dopamine , nmda receptor , acetylcholine , strychnine , endocrinology , medicine , adenosine , neurotransmitter , glutamate receptor , stimulation , dizocilpine , receptor , biology , biochemistry
Rat striatal slices, preincubated with [ 3 H]‐dopamine and [ 14 C]‐choline, were continuously superfused and electrically stimulated. Electrically evoked release of [ 3 H]‐dopamine and [ 14 C]‐acetylcholine (ACh) was not significantly changed by elimination of Mg 2+ from superfusion buffer, but the basal release of [ 3 H]‐dopamine was doubled. Kynurenic acid (100–800 μ M ) caused, in the absence but not presence of Mg 2+ , a concentration‐dependent decrease in the evoked release of these two transmitters. The addition of glycine reversed the inhibition of the evoked release of both transmitters caused by kynurenic acid (400 μ M ) in a concentration‐dependent manner. In addition, glycine increased the evoked release of [ 3 H]‐dopamine via a site inhibitable by strychnine (1 μ M ). Another two antagonists at N ‐methyl‐ D ‐aspartate (NMDA) receptors, 2‐amino‐5‐phosphonovaleric acid and dizocilpine, also decreased significantly the evoked release of the two transmitters in a concentration‐dependent manner in the absence, but not presence of Mg 2+ . By contrast, an antagonist of non‐NMDA receptors, 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (10 μ M ) significantly decreased the evoked release of the two transmitters in the presence, but not in the absence of Mg 2+ . Electrical field stimulation evoked release of endogenous adenosine, and this release tended to be higher in the absence of Mg 2+ . However, the addition of a selective adenosine A 1 receptor antagonist 8‐cyclopentyl‐1,3‐dipropylxanthine (200 n M ) did not influence the evoked release of the two transmitters, showing that the released adenosine is of little importance in controlling ACh and dopamine release from striatal slices. Non‐NMDA receptors may play a similar role when Mg 2+ ions are present. The results indicate that NMDA receptors activated in the absence of Mg 2+ participate in the electrically‐evoked release of [ 3 H]‐dopamine and [ 14 C]‐ACh from the striatum.