title: PKCβ Inhibitors Attenuate Amphetamine-Stimulated Dopamine Efflux.
abstract: Amphetamine abuse afflicts over 13 million people, and there is currently no universally accepted treatment for amphetamine addiction. Amphetamine serves as a substrate for the dopamine transporter and reverses the transporter to cause an increase in extracellular dopamine. Activation of the beta subunit of protein kinase C (PKCβ) enhances extracellular dopamine in the presence of amphetamine by facilitating the reverse transport of dopamine and internalizing the D2 autoreceptor. We previously demonstrated that PKCβ inhibitors block amphetamine-stimulated dopamine efflux in synaptosomes from rat striatum in vitro. In this study, we utilized in vivo microdialysis in live, behaving rats to assess the effect of the PKCβ inhibitors, enzastaurin and ruboxistaurin, on amphetamine-stimulated locomotion and increases in monoamines and their metabolites. A 30 min perfusion of the nucleus accumbens core with 1 μM enzastaurin or 1 μM ruboxistaurin reduced efflux of dopamine and its metabolite 3-methoxytyramine induced by amphetamine by approximately 50%. The inhibitors also significantly reduced amphetamine-stimulated extracellular levels of norepinephrine. The stimulation of locomotor behavior by amphetamine, measured simultaneously with the analytes, was comparably reduced by the PKCβ inhibitors. Using a stable isotope label retrodialysis procedure, we determined that ruboxistaurin had no effect on basal levels of dopamine, norepinephrine, glutamate, or GABA. In addition, normal uptake function through the dopamine transporter was unaltered by the PKCβ inhibitors, as measured in rat synaptosomes. Our results support the utility of using PKCβ inhibitors to reduce the effects of amphetamine.
authors.affiliation: Department of Pharmacology, University of Michigan , 2301 MSRB III, 1150 W. Medical Center Drive, Ann Arbor, Michigan 48109-5632, United States.|Department of Chemistry, University of Michigan , 9300 North University Avenue, Ann Arbor, Michigan 48105, United States.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Zestos
authors.affiliation: Department of Pharmacology, University of Michigan , 2301 MSRB III, 1150 W. Medical Center Drive, Ann Arbor, Michigan 48109-5632, United States.
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Mikelman
authors.affiliation: Department of Pharmacology, University of Michigan , 2301 MSRB III, 1150 W. Medical Center Drive, Ann Arbor, Michigan 48109-5632, United States.|Department of Chemistry, University of Michigan , 9300 North University Avenue, Ann Arbor, Michigan 48105, United States.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Kennedy
authors.affiliation: Department of Pharmacology, University of Michigan , 2301 MSRB III, 1150 W. Medical Center Drive, Ann Arbor, Michigan 48109-5632, United States.
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Gnegy
mesh_terms: D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D017660:Autoreceptors / Q000378:metabolism; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D004298:Dopamine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D050483:Dopamine Plasma Membrane Transport Proteins / Q000187:drug effects* / Q000378:metabolism; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D008297:Male; D017551:Microdialysis / Q000379:methods; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism; D064546:Protein Kinase C beta / Q000037:antagonists & inhibitors*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D017207:Rats, Sprague-Dawley
chemical_list: D017660:Autoreceptors; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors; D047428:Protein Kinase Inhibitors; D000661:Amphetamine; D064546:Protein Kinase C beta; C001746:3-methoxytyramine; D004298:Dopamine
keywords: LCMS; Protein kinase C; amphetamine; catecholamine; dopamine; microdialysis