Carrier‐mediated efflux of [3H] dopamine and [3H]1‐methyl‐4‐phenylopyridine: Effects of ascorbic acid
- 1 February 1991
- Vol. 7 (2) , 99-105
- https://doi.org/10.1002/syn.890070203
Abstract
The carrier‐mediated efflux of [3H]1‐methyl‐4‐phenylpyridine (MPP+) and [3H] dopamine was examined in mouse striatal synaposomal p2 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 [3H] dopamine, externally present dopamine at concentration of 1.3 μM reduced the intrasynaprosomal concentration of [3H] dopamine by 50% (the ECR value) with 8 min of incubation. The ECR value of dopamine in promoting the efflux of [3H]MPP+ was only 0.15 μM. Similarly [3H] ascorbic acid was weaker in enhancing the efflux of dopamine (ECR > 2000 μM) than that of [3H] MPP+ (ECR = 567 μM). This effect of ascorbic acid on the efflux of [3H]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.Keywords
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