title: Transgenic elimination of high-affinity antidepressant and cocaine sensitivity in the presynaptic serotonin transporter.
abstract: Serotonin [i.e., 5-hydroxytryptamine (5-HT)]-targeted antidepressants are in wide use for the treatment of mood disorders, although many patients do not show a response or experience unpleasant side effects. Psychostimulants, such as cocaine and 3,4-methylenedioxymethamphetamine (i.e., "ecstasy"), also impact 5-HT signaling. To help dissect the contribution of 5-HT signaling to the actions of these and other agents, we developed transgenic mice in which high-affinity recognition of multiple antidepressants and cocaine is eliminated. Our animals possess a modified copy of the 5-HT transporter (i.e., SERT, slc6a4) that bears a single amino acid substitution, I172M, proximal to the 5-HT binding site. Although the M172 substitution does not impact the recognition of 5-HT, this mutation disrupts high-affinity binding of many competitive antagonists in transfected cells. Here, we demonstrate that, in M172 knock-in mice, basal SERT protein levels, 5-HT transport rates, and 5-HT levels are normal. However, SERT M172 mice display a substantial loss of sensitivity to the selective 5-HT reuptake inhibitors fluoxetine and citalopram, as well as to cocaine. Through a series of biochemical, electrophysiological, and behavioral assays, we demonstrate the unique properties of this model and establish directly that SERT is the sole protein responsible for selective 5-HT reuptake inhibitor-mediated alterations in 5-HT clearance, in 5-HT1A autoreceptor modulation of raphe neuron firing, and in behaviors used to predict the utility of antidepressants.
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
authors.forename: Brent J
authors.initials: BJ
authors.lastname: Thompson
authors.forename: Tammy
authors.initials: T
authors.lastname: Jessen
authors.forename: L K
authors.initials: LK
authors.lastname: Henry
authors.forename: Julie R
authors.initials: JR
authors.lastname: Field
authors.forename: Karen L
authors.initials: KL
authors.lastname: Gamble
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Gresch
authors.forename: Ana M
authors.initials: AM
authors.lastname: Carneiro
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Horton
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Chisnell
authors.forename: Yekaterina
authors.initials: Y
authors.lastname: Belova
authors.forename: Douglas G
authors.initials: DG
authors.lastname: McMahon
authors.forename: Lynette C
authors.initials: LC
authors.lastname: Daws
authors.forename: Randy D
authors.initials: RD
authors.lastname: Blakely
mesh_terms: D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects; D003042:Cocaine / Q000494:pharmacology*; D055879:Gene Knock-In Techniques; D066298:In Vitro Techniques; D007700:Kinetics; D051379:Mice; D008822:Mice, Transgenic; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000378:metabolism*; D011903:Raphe Nuclei / Q000187:drug effects / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D017367:Selective Serotonin Reuptake Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
chemical_list: D000928:Antidepressive Agents; D003042:Cocaine; D012701:Serotonin; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors