BACKGROUND:Drugaddictioninvolvestwomaincentralnervoussystems,namelythedopamineandnoradrenalinesystems.Thesesystemsareprimarilydistributedinfivebrainregions:theventraltegmentalarea,thenucleusaccumbens,theprefrontalcortex,thehippocampus,andthelocuscoeruleus.OBJECTIVE:Toinvestigateregionalchangesofguaninenucleotidebindingprotein-inhabitant2(Gi2)indopaminergicandnoradrenergicneuronsinbrainsofmorphine-tolerantand-dependentrats.DESIGN,TIME,ANDSETTING:ArandomizedcontrolstudywasperformedattheDepartmentofNeu-robiologyintheSecondMilitaryMedicalUniversityofChinesePLA(Shanghai,China)betweenSeptember2002andMarch2004.MATERIALS:Thirty-six,healthy,male,Sprague-Dawley(SD)ratswereusedtoestablishmorphine-dependentmodels.MorphinehydrochloridewasaproductofShenyangFirstPharmaceuticalFactory(China);naloxonehydrochloridewasaproductofBeijingFour-RingPharmaceuticalFactory(China);andαsubunitofGi2antibodywasofferedbySantaCruzBiotechnology,Inc(USA).METHODS:Thirty-sixSDratswererandomlypidedintosixgroups(n=6):(1)acutemor-phine-dependentgroup,(2)acuteabstinentgroup,(3)acutecontrolgroup,(4)chronicmorphine-dependentgroup,(5)chronicabstinentgroup,and(6)chroniccontrolgroup.Ratsintheacutemorphine-dependentandtheacutegroupswereinjectedwithmorphine(5mg/kg),oneinjectioneverytwohours,foratotalofeightinjections.Intheacuteandchronicmorphine-dependentratmodels,morphinewithdrawalsyndromewasprecipitatedbyaninjectionofnaloxone(5mg/kg).Ratsintheacutecontrolgroupweregivenaperitonealinjectionofphysiologicalsalineatthesameadministrationtimeastheabovetwogroups.Ratsinthechronicmorphine-dependentandchronicabstinentgroupswereinjectedwithmorphinethreetimesperday.Theadministrationdoseonday1wasinitially5mg/kgat20:00,whichincreasedby5mg/kgat8:00,12:00,and20:00untilday7.Onday
