DynorphinsReceptors, Opioid, kappaEndorphinsEnkephalinsReceptors, OpioidEnkephalin, LeucineNaltrexoneNeurokinin BEnkephalin, MethionineNarcotic AntagonistsOpioid PeptidesBenzeneacetamidesKisspeptinsProtein PrecursorsNaloxonePyrrolidinesbeta-EndorphinReceptors, Opioid, muArcuate NucleusSpinal CordHyperesthesiaReceptors, Opioid, deltaInjections, SpinalDiprenorphineLevorphanolEnkephalin, Leucine-2-AlanineEnkephalin, D-Penicillamine (2,5)-Analgesics, OpioidNeuronsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-NarcoticsRats, Sprague-DawleyPeptide FragmentsReceptors, Neurokinin-3GalaninSubstance PBenzomorphansAnalgesics, Non-NarcoticPain MeasurementNeuropeptidesHypothalamusAzocinesTrigeminal NerveEtorphineBrain ChemistryGuinea PigsDose-Response Relationship, DrugCorticotropin-Releasing HormoneAnalgesicsDizocilpine MaleateHyperalgesiaCorpus StriatumKallidinRadioimmunoassayPituitary GlandN-MethylaspartateHippocampusNerve FibersPainSupraoptic NucleusNeurotransmitter AgentsReceptors, N-Methyl-D-AspartateOligopeptidesImmunochemistryPosterior Horn CellsPain ThresholdBehavior, AnimalBrainCocaineDiterpenes, ClerodaneReflex, AbdominalInjections, IntraventricularNeostriatumImmune SeraExcitatory Amino AcidsAmino Acid SequenceSwimmingPeptidesSubstance Withdrawal SyndromeMorphineGonadotropin-Releasing HormoneGlobus PallidusNucleus AccumbensDrug ToleranceReceptors, Amino AcidLearning DisordersMicrodialysisProto-Oncogene Proteins c-fos