NaltrexoneNaloxoneNarcotic AntagonistsReceptors, OpioidReceptors, Opioid, muAnalgesics, OpioidReceptors, Opioid, deltaReceptors, Opioid, kappaOpioid PeptidesMorphineEndorphinsNarcoticsOpioid-Related DisordersEnkephalinsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Dose-Response Relationship, DrugEnkephalin, MethionineBuprenorphineDynorphinsbeta-EndorphinSubstance Withdrawal SyndromeEnkephalin, LeucineMorphinansDiprenorphinePyrrolidinesEnkephalin, Leucine-2-AlanineRats, Sprague-DawleyMorphine DependenceAnalgesicsEnkephalin, D-Penicillamine (2,5)-BenzeneacetamidesPiperidinesPain MeasurementAzocinesHeroinDrug InteractionsHistamine H2 AntagonistsBenzomorphansFentanylPainDrug ToleranceSerotonin 5-HT3 Receptor AntagonistsLevorphanolExcitatory Amino Acid AntagonistsOligopeptidesDopamine AntagonistsRadioligand AssayEtorphinePruritusOxymorphoneBenzylidene CompoundsInjections, IntraventricularHistamine AntagonistsInjections, SpinalAlcoholismTime FactorsEthanolMeptazinolBinding, CompetitiveHeroin DependenceAnalgesics, Non-NarcoticLigandsBehavior, AnimalSpiro CompoundsConditioning, OperantAnalgesiaNalorphineCalcium Channel BlockersReceptors, N-Methyl-D-AspartateBrainReceptors, EndothelinRats, WistarHydromorphoneMethadyl AcetateAdrenergic alpha-AntagonistsPain ThresholdDiterpenes, ClerodaneDisease Models, AnimalPeriaqueductal GrayReceptor, Endothelin ANalbuphineDrug Inverse AgonismMethadoneSelf AdministrationNociceptorsDizocilpine MaleateAntipruriticsGuinea PigsInjections, SubcutaneousReceptors, VasopressinReceptor, Endothelin BHormone AntagonistsTaurineSpinal CordTetrahydroisoquinolinesHyperalgesiaMotor ActivityMice, Inbred ICRSomatostatinRanitidine