title: Repeated amphetamine couples norepinephrine transporter and calcium channel activities in PC12 cells.
abstract: Repeated intermittent amphetamine enhances efflux of dopamine through the dopamine transporter in rat basal ganglia and through the norepinephrine transporter in rat pheochromocytoma PC12 cells. Extracellular Ca2+ is required for the detection of this enhancement in the rat. In this study, we examined the role of Ca2+ and Ca2+ channels in the enhanced amphetamine-induced dopamine efflux that develops in PC12 cells following repeated intermittent amphetamine. Repeated pretreatment of PC12 cells with 1 microM amphetamine followed by a drug-free period increased amphetamine-induced efflux of dopamine compared with controls. The enhancement in amphetamine-induced dopamine efflux depended upon the presence of extracellular Ca2+ and was inhibited by the blockade of N-type and L-type Ca2+ channels. The enhanced dopamine efflux was not altered by tetanus toxin or reserpine, treatments that abrogate synaptic vesicle-mediated, exocytotic dopamine efflux. Measurement of intracellular Ca2+ concentrations using fura-2/acetoxymethyl ester revealed that amphetamine increased intracellular Ca2+ by a transporter-dependent mechanism. In amphetamine-pretreated cells, amphetamine elicited a greater increase in intracellular Ca2+; this increase depended upon the presence of extracellular Ca2+ and N- and L-type Ca2+ channel activity. The enhanced amphetamine-induced dopamine efflux requires Ca2+/calmodulin kinase activity. In vehicle-treated cells, 1 microM amphetamine inhibited the calmodulin kinase activity although it did not in amphetamine-pretreated cells. This study suggests that repeated intermittent amphetamine couples norepinephrine transporter activity and Ca2+ signaling.
authors.affiliation: Department of Pharmacology, 2220E Medical Science Research Building III, University of Michigan Medical School, Ann Arbor, MI 48109-0632, USA.
authors.forename: L
authors.initials: L
authors.lastname: Kantor
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: B
authors.initials: B
authors.lastname: Guptaroy
authors.forename: Y H
authors.initials: YH
authors.lastname: Park
authors.forename: M E
authors.initials: ME
authors.lastname: Gnegy
mesh_terms: D018663:Adrenergic Agents / Q000378:metabolism / Q000494:pharmacology*; D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology; D000661:Amphetamine / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D050484:Norepinephrine Plasma Membrane Transport Proteins; D016716:PC12 Cells; D051381:Rats; D012110:Reserpine / Q000494:pharmacology; D027981:Symporters / Q000378:metabolism*; D013744:Tetanus Toxin / Q000494:pharmacology
chemical_list: D018663:Adrenergic Agents; D018759:Adrenergic Uptake Inhibitors; D015220:Calcium Channels; D050484:Norepinephrine Plasma Membrane Transport Proteins; C493226:Slc6a2 protein, rat; D027981:Symporters; D013744:Tetanus Toxin; D012110:Reserpine; D000661:Amphetamine; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium; D004298:Dopamine