Heroin DependenceAnalgesicsMethadoneHeroinNarcoticsBuprenorphineNuclear Receptor Subfamily 4, Group A, Member 2Receptors, Opioid, muBehavior, AddictiveCryptochromesLinkage DisequilibriumGene FrequencySubstance-Related DisordersGenetic Predisposition to DiseaseGenetic TestingHaplotypesOpioid-Related DisordersSelf AdministrationPolymorphism, Single NucleotideMorphine DerivativesGenotypeCocaineSubstance Withdrawal SyndromeStreet DrugsSubstance Abuse Treatment CentersRewardDrug OverdoseAnalgesics, OpioidNucleus AccumbensOpiate Substitution TreatmentCodeineTobacco Use DisorderConditioning, OperantMorphineSubstance Abuse, IntravenousSubstance Abuse DetectionReinforcement (Psychology)Dopamine Uptake InhibitorsDrug and Narcotic ControlNaltrexoneNaloxoneDrug-Seeking BehaviorAlcoholismCompulsive BehaviorCocaine-Related DisordersDrug UsersDopamineBehavior, AnimalMotivationAmphetamine-Related Disorders