CocaineSynaptic TransmissionMorphineExcitatory Postsynaptic PotentialsDopamine Uptake InhibitorsSynapsesCocaine-Related DisordersHippocampusRats, Sprague-DawleyElectric StimulationEvoked PotentialsNeuronsPatch-Clamp TechniquesSelf AdministrationMorphine DependencePresynaptic TerminalsDose-Response Relationship, DrugMorphine DerivativesGlutamic AcidNeuronal PlasticityLong-Term PotentiationExcitatory Amino Acid AntagonistsReceptors, N-Methyl-D-Aspartategamma-Aminobutyric AcidReceptors, AMPANeural InhibitionAction PotentialsNeurotransmitter AgentsMethoxyfluraneConditioning, OperantEther6-Cyano-7-nitroquinoxaline-2,3-dioneNucleus AccumbensElectrophysiologyBehavior, AnimalRats, WistarSynaptic VesiclesAnalgesics, OpioidPyramidal CellsReinforcement ScheduleNeuromuscular JunctionDopamineTime FactorsNarcoticsMotor NeuronsMotor ActivityMembrane PotentialsCrack CocaineReinforcement (Psychology)Drug ToleranceAnimals, NewbornCalciumCorpus StriatumColumbidaeNaloxoneAdenosineDrug InteractionsVentral Tegmental AreaDopamine AgonistsReceptors, Dopamine D2Receptors, Opioid, muCells, CulturedDisease Transmission, InfectiousInhibitory Postsynaptic PotentialsRewardExtinction, PsychologicalAnalysis of VarianceRats, Long-EvansSubstance Withdrawal SyndromeBrainNarcotic AntagonistsMicrodialysisInfectious Disease Transmission, VerticalCentral Nervous System StimulantsExcitatory Amino Acid AgonistsReceptors, Metabotropic GlutamateReceptors, GlutamateGABA AntagonistsPrenatal Exposure Delayed EffectsMicroscopy, Electron, TransmissionHeroin2-Amino-5-phosphonovalerateNorepinephrinePain MeasurementSpinal CordAnalgesiaMiniature Postsynaptic PotentialsCodeineInjections, SpinalPregnancyNerve Tissue Proteinsalpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic AcidReceptors, GABA-APainSynaptic PotentialsBicucullinePeriaqueductal GrayBehavior, AddictiveAnalgesicsLong-Term Synaptic Depression