title: Amphetamine activates calcium channels through dopamine transporter-mediated depolarization.
abstract: Amphetamine (AMPH) and its more potent enantiomer S(+)AMPH are psychostimulants used therapeutically to treat attention deficit hyperactivity disorder and have significant abuse liability. AMPH is a dopamine transporter (DAT) substrate that inhibits dopamine (DA) uptake and is implicated in DA release. Furthermore, AMPH activates ionic currents through DAT that modify cell excitability presumably by modulating voltage-gated channel activity. Indeed, several studies suggest that monoamine transporter-induced depolarization opens voltage-gated Ca(2+) channels (CaV), which would constitute an additional AMPH mechanism of action. In this study we co-express human DAT (hDAT) with Ca(2+) channels that have decreasing sensitivity to membrane depolarization (CaV1.3, CaV1.2 or CaV2.2). Although S(+)AMPH is more potent than DA in transport-competition assays and inward-current generation, at saturating concentrations both substrates indirectly activate voltage-gated L-type Ca(2+) channels (CaV1.3 and CaV1.2) but not the N-type Ca(2+) channel (CaV2.2). Furthermore, the potency to achieve hDAT-CaV electrical coupling is dominated by the substrate affinity on hDAT, with negligible influence of L-type channel voltage sensitivity. In contrast, the maximal coupling-strength (defined as Ca(2+) signal change per unit hDAT current) is influenced by CaV voltage sensitivity, which is greater in CaV1.3- than in CaV1.2-expressing cells. Moreover, relative to DA, S(+)AMPH showed greater coupling-strength at concentrations that induced relatively small hDAT-mediated currents. Therefore S(+)AMPH is not only more potent than DA at inducing hDAT-mediated L-type Ca(2+) channel currents but is a better depolarizing agent since it produces tighter electrical coupling between hDAT-mediated depolarization and L-type Ca(2+) channel activation.
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States.
authors.forename: Krasnodara N
authors.initials: KN
authors.lastname: Cameron
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Solis
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States.
authors.forename: Iwona
authors.initials: I
authors.lastname: Ruchala
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States.
authors.forename: Louis J
authors.initials: LJ
authors.lastname: De Felice
authors.affiliation: Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, United States. Electronic address: jmeltit@vcu.edu.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Eltit
mesh_terms: D000661:Amphetamine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D015220:Calcium Channels / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008564:Membrane Potentials
chemical_list: D002120:Calcium Channel Agonists; D015220:Calcium Channels; D050483:Dopamine Plasma Membrane Transport Proteins; D000661:Amphetamine; D002118:Calcium
keywords: Excitability; L-type Ca(2+) channels; MDMA; Monoamine transporters; Neurotransmitter transport; Serotonin; Stimulants