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Carrier‐mediated efflux of [ 3 H] dopamine and [ 3 H]1‐methyl‐4‐phenylopyridine: Effects of ascorbic acid
Author(s) -
Debler Edumund A.,
Sershen Henry,
Hashim Audrey,
Lajtha Abel,
Reith Maarten E. A.
Publication year - 1991
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.890070203
Subject(s) - dopamine , mazindol , ascorbic acid , efflux , chemistry , d 1 , biochemistry , endocrinology , receptor , biology , food science
The carrier‐mediated efflux of [ 3 H]1‐methyl‐4‐phenylpyridine (MPP + ) and [ 3 H] dopamine was examined in mouse striatal synaposomal p 2 fractions. Although the two compound are transported by the same carrier, the translocation of the carrier–ligand complex is more rapid with MPP + than with dopamine. With dopamine‐stimulated efflux of preloaded [ 3 H] dopamine, externally present dopamine at concentration of 1.3 μM reduced the intrasynaprosomal concentration of [ 3 H] dopamine by 50% (the EC R value) with 8 min of incubation. The EC R value of dopamine in promoting the efflux of [ 3 H]MPP + was only 0.15 μM. Similarly [ 3 H] ascorbic acid was weaker in enhancing the efflux of dopamine (EC R > 2000 μM) than that of [ 3 H] MPP + (EC R = 567 μM). This effect of ascorbic acid on the efflux of [ 3 H]MPP + was attenuated by mazindol, a blocker of dopamine uptake. It is proposed that ascorbic acid has a neuromodulatory role involving changes at the level of carrier‐membrane translocation and/or orientation.