title: Cocaine modulates mammalian circadian clock timing by decreasing serotonin transport in the SCN.
abstract: Cocaine abuse disrupts reward and homeostatic processes through diverse processes, including those involved in circadian clock regulation. Recently we showed that cocaine administration to mice disrupts nocturnal photic phase resetting of the suprachiasmatic (SCN) circadian clock, whereas administration during the day induces non-photic phase shifts. Importantly, the same effects are seen when cocaine is applied to the SCN in vitro, where it blocks photic-like (glutamate-induced) phase shifts at night and induces phase advances during the day. Furthermore, our previous data suggest that cocaine acts in the SCN by enhancing 5-HT signaling. For example, the in vitro actions of cocaine mimic those of 5-HT and are blocked by the 5-HT antagonist, metergoline, but not the dopamine receptor antagonist, fluphenazine. Although our data are consistent with cocaine acting through enhanced 5-HT signaling, the nonselective actions of cocaine as an antagonist of monoamine transporters raises the question of whether inhibition of the 5-HT transporter (SERT) is key to its circadian effects. Here we investigate this issue using transgenic mice expressing a SERT that exhibits normal 5-HT recognition and transport but significantly reduced cocaine potency (SERT Met172). Circadian patterns of SCN behavioral and neuronal activity did not differ between wild-type (WT) and SERT Met172 mice, nor did they differ in the ability of the 5-HT1A,2,7 receptor agonist, 8-OH-DPAT to reset SCN clock phase, consistent with the normal SERT expression and activity in the transgenic mice. However, (1) cocaine administration does not induce phase advances when administered in vivo or in vitro in SERT Met172 mice; (2) cocaine does not block photic or glutamate-induced phase shifts in SERT Met172 mice; and (3) cocaine does not induce long-term changes in free-running period in SERT Met172 mice. We conclude that SERT antagonism is required for the phase shifting of the SCN circadian clock induced by cocaine.
authors.affiliation: Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA. Electronic address: rprosser@utk.edu.
authors.forename: R A
authors.initials: RA
authors.lastname: Prosser
authors.affiliation: Department of Biological Sciences, Kent State University, Kent, OH 44242, USA.
authors.forename: A
authors.initials: A
authors.lastname: Stowie
authors.affiliation: Department of Biological Sciences, Kent State University, Kent, OH 44242, USA.
authors.forename: M
authors.initials: M
authors.lastname: Amicarelli
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232-8548, USA; Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN 37232-8548, USA.
authors.forename: A G
authors.initials: AG
authors.lastname: Nackenoff
authors.affiliation: Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232-8548, USA; Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN 37232-8548, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Blakely
authors.affiliation: Department of Biological Sciences, Kent State University, Kent, OH 44242, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Glass
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D057906:Circadian Clocks / Q000187:drug effects*; D002940:Circadian Rhythm / Q000187:drug effects*; D003042:Cocaine / Q000494:pharmacology*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D051379:Mice; D008822:Mice, Transgenic; D012701:Serotonin / Q000378:metabolism*; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013493:Suprachiasmatic Nucleus / Q000187:drug effects* / Q000378:metabolism
chemical_list: D018765:Dopamine Uptake Inhibitors; D050486:Serotonin Plasma Membrane Transport Proteins; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D003042:Cocaine
keywords: circadian rhythms; cocaine; glutamate; phase-shift; serotonin; suprachiasmatic nucleus