title: Evaluation of antidepressant-related behavioral responses in mice lacking the serotonin transporter.
abstract: Inhibition of the serotonin transporter (5-HTT) is a principal initial target of many antidepressants. However, the contribution of the 5-HTT to their therapeutic efficacy is incompletely understood. We utilized a targeted gene mutation approach to examine the role of the 5-HTT in the behavioral actions of antidepressants. The 5-HTT mutation was bred onto two separate genetic backgrounds, C57BL/6J and 129S6. On a preliminary screen for gross physical, neurological and behavioral functions, all measures were normal with the exception that 5-HTT -/- mice on the C57BL/6J background showed increased body weight and poor rotarod performance, and 5-HTT -/- mice on the 129S6 background showed reduced neuromuscular strength. On the tail suspension test, 5-HTT -/- mice on the 129S6 background showed a baseline antidepressant-like reduction in immobility. In contrast, the same mice showed increased immobility in the forced swim test, possibly due to compromised neuromuscular strength. 5-HTT -/- mice on the C57BL/6J background showed no baseline antidepressant-related phenotype on either test. The behavioral effects of three antidepressants were tested in 5-HTT mutant mice (C57BL/6J background) in the tail suspension test. The anti-immobility effects of the serotonin reuptake inhibitor, fluoxetine (30 mg/kg), were abolished in 5-HTT -/- mice, confirming that the 5-HTT gene is required for the behavioral effects of fluoxetine. In contrast, 5-HTT-/- mice retained sensitivity to the anti-immobility effects of the norepinephrine reuptake inhibitor, desipramine (20 mg/kg), and the mixed serotonin/norepinephrine reuptake inhibitor, imipramine (25 mg/kg). 5-HTT knockout mice provide a valuable tool for delineating the neuropsychopharmacological actions of antidepressants.
authors.affiliation: Section on Behavioral Genomics, National Institute of Mental Health, NIH, Bethesda, MD 20892-1375, USA. aholmes@intra.nimh.nih.gov
authors.forename: Andrew
authors.initials: A
authors.lastname: Holmes
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Yang
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Murphy
authors.forename: Jacqueline N
authors.initials: JN
authors.lastname: Crawley
mesh_terms: D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics*; D005260:Female; D007103:Immobilization; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D026901:Membrane Transport Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins; D050486:Serotonin Plasma Membrane Transport Proteins
chemical_list: D000928:Antidepressive Agents; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050486:Serotonin Plasma Membrane Transport Proteins; C493231:Slc6a4 protein, mouse