title: Brain mu-opioid receptor binding: relationship to relapse to cocaine use after monitored abstinence.
abstract: BACKGROUND
  Cocaine users have increased regional brain mu-opioid receptor (mOR) binding which correlates with cocaine craving. The relationship of mOR binding to relapse is unknown.
  
  
  OBJECTIVE
  To evaluate regional brain mOR binding as a predictor of relapse to cocaine use is the objective of the study.
  
  
  METHODS
  Fifteen nontreatment-seeking, adult cocaine users were housed on a closed research ward for 12 weeks of monitored abstinence and then followed for up to 1 year after discharge. Regional brain mOR binding was measured after 1 and 12 weeks using positron emission tomography (PET) with [11C]carfentanil (a selective mOR agonist). Time to first cocaine use (lapse) and to first two consecutive days of cocaine use (relapse) after discharge was based on self-report and urine toxicology.
  
  
  RESULTS
  A shorter interval before relapse was associated with increased mOR binding in frontal and temporal cortical regions at 1 and 12 weeks of abstinence (Ps < 0.001) and with a lesser decrease in binding between 1 and 12 weeks (Ps < 0.0008). There were significant positive correlations between mOR binding at 12 weeks and percent days of cocaine use during first month after relapse (Ps < 0.002). In multiple linear regression analysis, mOR binding contributed significantly to the prediction of time to relapse (R2= 0.79, P < 0.001), even after accounting for clinical variables.
  
  
  CONCLUSIONS
  Increased brain mOR binding in frontal and temporal cortical regions is a significant independent predictor of time to relapse to cocaine use, suggesting an important role for the brain endogenous opioid system in cocaine addiction.
authors.affiliation: Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA. dgorelic@mail.nih.gov
authors.forename: David A
authors.initials: DA
authors.lastname: Gorelick
authors.forename: Yu Kyeong
authors.initials: YK
authors.lastname: Kim
authors.forename: Badreddine
authors.initials: B
authors.lastname: Bencherif
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Boyd
authors.forename: Richard
authors.initials: R
authors.lastname: Nelson
authors.forename: Marc L
authors.initials: ML
authors.lastname: Copersino
authors.forename: Robert F
authors.initials: RF
authors.lastname: Dannals
authors.forename: J James
authors.initials: JJ
authors.lastname: Frost