Abstract
The stimulant drug amphetamine is postulated to enhance dopamine release through the plasmalemmal dopamine transporter by an exchange diffusion with synaptosomal dopamine. Because protein kinase C has been shown to have an effect on dopamine transporter activity, we examined the effect of protein kinase C inhibitors on endogenous dopamine release stimulated by amphetamine in perfused rat striatal slices. At concentrations of 1 μM, the selective protein kinase C inhibitors chelerythrine, Ro31–8220 and calphostin C nearly completely inhibited endogenous dopamine release elicited by 1 μM amphetamine. The inactive analog bisindoylmaleimide V had no effect. Extracellular Ca++ was not required for the effect of the inhibitors. The importance of vesicular dopamine release was examined by determining inhibitor activity in reserpine-treated rats. Dopamine release elicited by 1 μM amphetamine was not significantly altered in reserpine-treated rats compared with control animals. Ro31–8220 at 1 μM completely blocked amphetamine-induced dopamine release in reserpine-treated rats. Activation of protein kinase C with 250 nM of the phorbol ester 12-O-tetradecanoylphorbol 13-acetate increased dopamine release, and the release was not additive with 1 μM amphetamine. Both chelerythrine and Ro31–8220 at 1 μM increased [3H]dopamine uptake by 17% and 30%, respectively, whereas a brief exposure to 12-O-tetradecanoylphorbol 13-acetate slightly inhibited [3H]dopamine uptake. Our results suggest that amphetamine-mediated dopamine release through the plasmalemmal transporter is highly dependent on protein kinase C activity.
Footnotes
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Send reprint requests to: Dr. Margaret E. Gnegy, 2220E MSRB III, Department of Pharmacology, The University of Michigan Medical School, Ann Arbor, MI 48109-0632. E-mail: pgnegy{at}umich.edu
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↵1 This work was supported by Grant DA-05066 from the National Institutes for Drug Abuse and NIDA Interdisciplinary Training Grant DA-07267 at the University of Michigan Substance Abuse Research Center (L.K.).
- Abbreviations:
- AMPH
- amphetamine
- DA
- dopamine
- DMSO
- dimethylsulfoxide
- GAP-43
- growth-associated protein
- HPLC
- high-performance liquid chromatography
- KRB
- Krebs-Ringer buffer
- PKC
- protein kinase C
- TPA
- 12-O-tetradecanoylphorbol-13-acetate
- ANOVA
- analysis of variance
- Received June 10, 1997.
- Accepted October 16, 1997.
- The American Society for Pharmacology and Experimental Therapeutics
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