Adenosine2-ChloroadenosineAdenosine-5'-(N-ethylcarboxamide)Receptor, Adenosine A2AAnalgesicsInjections, SpinalReceptor, Adenosine A1PhenylisopropyladenosineReceptors, Purinergic P1Pain MeasurementAnalgesics, OpioidAdenosine KinaseAdenosine DeaminaseTubercidinReceptor, Adenosine A2BReceptor, Adenosine A3Receptors, Opioid, muPainMorphineReceptors, PurinergicNarcotic AntagonistsXanthinesAdenosine A2 Receptor AgonistsPurinergic P1 Receptor AgonistsNaltrexoneAnalgesiaDose-Response Relationship, DrugPeriaqueductal GrayAdenosine A1 Receptor AntagonistsPurinergic P1 Receptor AntagonistsAdenosine A1 Receptor AgonistsToyocamycinReceptors, Opioid, deltaNaloxoneRats, Sprague-DawleyAnalgesics, Non-NarcoticReceptors, Opioidbeta-EndorphinReceptors, Adenosine A2Receptors, Opioid, kappaPain ThresholdPhenethylaminesAdenosine A2 Receptor AntagonistsTheophyllineSpinal CordHyperalgesiaCannabinoidsDeoxyadenosinesCyclic AMPInosineAdenosine MonophosphateFormycinsPiperidinesAdenineAdenosylhomocysteinaseAdenine NucleotidesDrug ToleranceInjections, IntraventricularDipyridamoleNucleosidesRibonucleosidesKineticsThioinosineAdministration, OralAdenosine A3 Receptor AntagonistsAdenylate CyclasePurinesLucanthoneNociceptorsAdenosine A3 Receptor AgonistsRats, Inbred Strains1-Methyl-3-isobutylxanthineStructure-Activity RelationshipDideoxyadenosine5'-NucleotidaseTrypanosomatinaAdenosine Deaminase InhibitorsNociceptionOpioid PeptidesEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Rats, WistarEnzyme InhibitorsVasodilator AgentsCells, CulturedTime FactorsEnkephalinsAdenosine TriphosphatasesLeishmania mexicanaEnkephalin, D-Penicillamine (2,5)-Mice, Inbred ICRGuinea PigsColforsinAdrenergic alpha-2 Receptor AgonistsRibonucleotidesMorphinansDichlororibofuranosylbenzimidazoleDrug Administration RoutesTrypanocidal AgentsNucleoside DeaminasesDynorphins