title: Circadian rhythmicity in serotonin transporter knockout mice.
abstract: OBJECTIVE
  Serotonin transporter knockout (5-HTT KO) mice exhibit elevated basal extracellular serotonin, increased depressive-like behaviors and increased rapid eye movement sleep. Because abnormalities of circadian rhythms are associated with mood disorders, we tested the hypothesis that 5-HTT KO mice would have altered circadian rhythmicity.
  
  
  METHODS
  Homecage locomotor activity was recorded in wild-type (WT) and KO mice under a standard 12:12 light-dark cycle. After 4weeks of recording, mice received a one-hour light pulse at circadian time (CT) 14 and then were kept under constant darkness for 3weeks.
  
  
  RESULTS
  There were no significant differences in amplitude, period, acrophase or total home cage locomotor activity between WT and KO mice during the 12:12 light-dark cycle or during constant darkness. The mean phase delay to a CT 14 light pulse was significantly attenuated in KO compared to WT mice.
  
  
  CONCLUSIONS
  Acute increases in serotonin have been reported to attenuate photic phase shifts. The current study demonstrates that this effect is maintained in the face of a lifelong absence of 5-HTT.
authors.affiliation: Graduate Program in Neuroscience, University of Southern California, United States. Electronic address: rpang@usc.edu.
authors.forename: Raina D
authors.initials: RD
authors.lastname: Pang
authors.affiliation: Graduate Program in Neuroscience, University of Southern California, United States; Department of Psychiatry and Behavioral Science, University of Southern California, United States; Department of Neurology, University of Southern California, United States; Department of Biomedical Engineering, University of Southern California, United States; Department of Cell and Neurobiology, University of Southern California, United States.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Holschneider
authors.affiliation: Department of Cell and Neurobiology, University of Southern California, United States.
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Miller
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D045604:Extracellular Fluid / Q000737:chemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout / Q000235:genetics / Q000502:physiology*; D009043:Motor Activity / Q000235:genetics / Q000502:physiology; D017440:Photoperiod; D012701:Serotonin / Q000032:analysis / Q000502:physiology; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics / Q000502:physiology*; D013997:Time Factors
chemical_list: D050486:Serotonin Plasma Membrane Transport Proteins; D012701:Serotonin