title: Elevated tph2 mRNA expression in a rat model of chronic anxiety.
abstract: BACKGROUND
  Allelic variations in TPH2, the gene encoding tryptophan hydroxylase 2, the rate-limiting enzyme for brain serotonin (5-HT) biosynthesis, may be genetic predictors of panic disorder and panic responses to panicogenic challenges in healthy volunteers. To test the hypothesis that tph2 mRNA is altered in chronic anxiety states, we measured tph2 expression in an established rat model of panic disorder.
  
  
  METHODS
  We implanted 16 adult, male rats with bilateral guide cannulae and then primed them with daily injections of the corticotropin-releasing factor (CRF) receptor agonist, urocortin 1 (UCN1, 6 fmoles/100 nl per side, n = 8) or vehicle (n = 8) into the basolateral amygdaloid complex (BL) for 5 consecutive days. Anxiety-like behavior was assessed, 24 hr prior to and 48 hr following priming, in the social interaction (SI) test. A third group (n = 7) served as undisturbed home cage controls. All rats were killed 3 days after the last intra-BL injection to analyze tph2 and slc6a4 (gene encoding the serotonin transporter, SERT) mRNA expression in the dorsal raphe nucleus (DR), the main source of serotonergic projections to anxiety-related brain regions, using in situ hybridization histochemistry.
  
  
  RESULTS
  UCN1 priming increased anxiety-related behavior in the SI test compared to vehicle-injected controls and elevated tph2, but not slc6a4, mRNA expression in DR subregions, including the ventrolateral DR/ventrolateral periaqueductal gray (DRVL/VLPAG), a subregion previously implicated in control of panic-related physiologic responses. Tph2 mRNA expression in the DRVL/VLPAG was correlated with increased anxiety-related behavior.
  
  
  CONCLUSIONS
  Our data support the hypothesis that chronic anxiety states are associated with dysregulated tph2 expression.
authors.affiliation: Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, Colorado 80309–0354, USA. nina.donner@colorado.edu
authors.forename: Nina C
authors.initials: NC
authors.lastname: Donner
authors.forename: Philip L
authors.initials: PL
authors.lastname: Johnson
authors.forename: Stephanie D
authors.initials: SD
authors.lastname: Fitz
authors.forename: Karen E
authors.initials: KE
authors.lastname: Kellen
authors.forename: Anantha
authors.initials: A
authors.lastname: Shekhar
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Lowry
mesh_terms: D000679:Amygdala / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D001008:Anxiety Disorders / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis*; D011903:Raphe Nuclei / Q000201:enzymology / Q000378:metabolism* / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D014365:Tryptophan Hydroxylase / Q000235:genetics*; D015854:Up-Regulation / Q000502:physiology
chemical_list: D012333:RNA, Messenger; D050486:Serotonin Plasma Membrane Transport Proteins; C493232:Slc6a4 protein, rat; D014365:Tryptophan Hydroxylase; C504569:tph2 protein, rat