title: High anxiety is a predisposing endophenotype for loss of control over cocaine, but not heroin, self-administration in rats.
abstract: BACKGROUND
  Although high anxiety is commonly associated with drug addiction, its causal role in this disorder is unclear.
  
  
  OBJECTIVE
  In light of strong evidence for dissociable neural mechanisms underlying heroin and cocaine addiction, the present study investigated whether high anxiety predicts the propensity of rats to lose control over intravenous cocaine or heroin self-administration.
  
  
  METHODS
  Sixty-four rats were assessed for anxiety in the elevated plus-maze, prior to extended access to intravenous cocaine or heroin self-administration.
  
  
  RESULTS
  High-anxious rats, identified in the lower quartile of the population, showed a greater escalation of cocaine, but not heroin, self-administration compared with low-anxious rats selected in the upper quartile of the population. Anxiety scores were also positively correlated with the extent of escalation of cocaine self-administration.
  
  
  CONCLUSIONS
  The present data suggest that high anxiety predisposes rats to lose control over cocaine-but not heroin-intake. High anxiety may therefore be a vulnerability trait for the escalation of stimulant but not opiate self-administration.
authors.affiliation: Behavioural and Clinical Neuroscience Institute, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK.
authors.forename: Ruth
authors.initials: R
authors.lastname: Dilleen
authors.forename: Yann
authors.initials: Y
authors.lastname: Pelloux
authors.forename: Adam C
authors.initials: AC
authors.lastname: Mar
authors.forename: Anna
authors.initials: A
authors.lastname: Molander
authors.forename: Trevor W
authors.initials: TW
authors.lastname: Robbins
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Everitt
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Dalley
authors.forename: David
authors.initials: D
authors.lastname: Belin
mesh_terms: D000818:Animals; D001007:Anxiety / Q000150:complications / Q000503:physiopathology*; D003042:Cocaine / Q000008:administration & dosage*; D004195:Disease Models, Animal; D003932:Heroin / Q000008:administration & dosage*; D008297:Male; D018782:Maze Learning; D051381:Rats; D012646:Self Administration; D019966:Substance-Related Disorders / Q000209:etiology
chemical_list: D003932:Heroin; D003042:Cocaine