致幻剂与无羟色胺受体结合影响行为的方式

Neuron

Article

HallucinogensRecruitSpecific

Cortical5-HT2AReceptor-Mediated

SignalingPathwaystoAffectBehavior

JavierGonza´lez-Maeso,1,7NoeliaV.Weisstaub,3,4,5,7MingmingZhou,4PokmanChan,1LidijaIvic,1

RosalindAng,1AlenaLira,4MariaBradley-Moore,4YongchaoGe,1,2QiangZhou,1StuartC.Sealfon,1,2,*

andJayA.Gingrich4,5,6

1DepartmentofNeurology,MountSinaiSchoolofMedicine,NewYork,NY10029,USA2CenterforTranslationalSystemsBiology,MountSinaiSchoolofMedicine,NewYork,NY10029,USA3DepartmentofBiologicalSciences,ColumbiaUniversity,NewYork,NY10032,USA4DepartmentofPsychiatry,ColumbiaUniversity,NewYork,NY10032,USA5SacklerInstituteLaboratories,NewYorkStatePsychiatricInstitute,NewYork,NY10032,USA6LieberCenterforSchizophreniaResearch,NewYorkStatePsychiatricInstitute,NewYork,NY10032,USA7Theseauthorscontributedequallytothiswork.

*Correspondence:stuart.sealfon@mssm.edu

DOI10.1016/j.neuron.2007.01.008

SUMMARY

Hallucinogens,includingmescaline,psilocybin,

andlysergicaciddiethylamide(LSD),profoundly

affectperception,cognition,andmood.All

knowndrugsofthisclassare5-HT2Areceptor

(2AR)agonists,yetcloselyrelated2ARagonists

suchaslisuridelackcomparablepsychoactive

properties.Whyonlycertain2ARagonistsare

hallucinogensandwhichneuralcircuitsmediate

theireffectsarepoorlyunderstood.Bygeneti-

callyexpressing2ARonlyincortex,weshow

that2AR-regulatedpathwaysoncorticalneu-

ronsaresufficienttomediatethesignalingpat-

ternandbehavioralresponsetohallucinogens.

Hallucinogenicandnonhallucinogenic2AR

agonistsbothregulatesignalinginthesame

2AR-expressingcorticalneurons.However,

thesignalingandbehavioralresponsestothe

hallucinogensaredistinct.Whilelisurideand

LSDbothactat2ARexpressedbycortex

neuronstoregulatephospholipaseC,LSDre-

sponsesalsoinvolvepertussistoxin-sensitive

heterotrimericGi/oproteinsandSrc.These

studiesidentifythelong-elusiveneuralandsig-

nalingmechanismsresponsiblefortheunique

effectsofhallucinogens.

INTRODUCTION

Throughouthistory,naturallyoccurringhallucinogenic

substancessuchaspsilocybinandmescalinehavebeen

recognizedfortheircapacitytoalterperception,emotion,

andcognition(Nichols,2004).Allsuchhallucinogenic

compounds(HCs)exhibithighaffinityfor5-HT2Arecep-tors(2AR)(Gonzalez-MaesoandSealfon,2006;Roth

etal.,1998).Geneticorpharmacologicalinactivationof

2ARsignalingblocksthebehavioraleffectsofHCsin

avarietyofspecies,includingmice,rats,andhumans

(Fiorellaetal.,1995;Gonzalez-Maesoetal.,2003;Vollen-

weideretal.,1998).Takentogether,thesefindingsindi-

catethat2ARactivationisnecessaryforthepsychoactive

effectsofHCs.

ThedemonstrationthatHCselicittheirpsychoactive

effectsvia2ARactivationhasnotresolvedthefundamen-

talparadoxthat2ARactivationisauniversallyshared

propertyofHCsandthat2ARactivationisrequiredfor

HCeffects,butyetnotall2ARagonistsexhibithallucino-

genicactivity.Indeed,nonhallucinogeniccompounds

(NHCs)suchaslisurideandergotaminesharesignificant

structuralsimilaritiesandcomparableagonistactivities

at2AR(Eganetal.,1998),butlackpsychoactiveproper-

ties(Pierietal.,1978).

2ARisexpressedwidelyinthecentralnervoussystem

(CNS)andisexpressedinstructuresinvolvedinpsycho-

sis—theventralstriatumandventraltegmentalarea(Li

etal.,2004;Lopez-Gimenezetal.,1997,2001;Nocjar

etal.,2002;Pazosetal.,1985).Severalofthesestructures

havealsobeenimplicatedinHCeffects(Nielsenand

Scheel-Kruger,1986;Vetulanietal.,1979;Willinsand

Meltzer,1997).However,theneuronalsubstratesthat

mediatehallucinogeneffectsremainobscure.

OurpreviousstudyoftwoHCs,lysergicaciddi-

ethylamide(LSD)and1-(2,5-dimethoxy-4-iodophenyl)-2-

aminopropane(DOI),suggeststhehypothesisthatHCs

induceacharacteristic,2AR-dependentregulationofgene

expressioninmousesomatosensorycortex(SSC)(Gon-

zalez-Maesoetal.,2003).Byextendingourprevious

biochemicalstudiestoalargegroupofdiversechemicals,

weprovideabasisforpredictinghallucinogenicpotential

fromeffectsinmouse.WefindthatHCandNHC2AR

agonistsdifferintheirregulationofsignalingandphysiol-

ogyinthesameneuronsinvivoandinvitro.By

using

Neuron53,439–452,February1,2007ª2007ElsevierInc.439ageneticstrategytorestorespecifically2AR-signaling

capacitytocorticalneuronsinhtr2AÀ/Àmice,weshow

thattheuniquesignalingandneurobehavioraleffectsof

HCsdonotresultfromtheirpreviouslyproposedregula-

tionofsubcortical-corticalcircuits,butareintrinsicto

2AR-expressingcorticalpyramidalneurons.Weformulate

anewmodelforthemechanismofactionofHCs.

RESULTS

HCsAre2ARLigandsintheMouse

TheresponsestoHCandNHC2ARagonistshavepre-

dominantlybeenstudiedinrats,primates,andhumans.

Theeffectsofthesedrugsinmicehavebeenlesswell

studied.Becausehallucinogensrequire2ARactivation,

wesoughttoverifythatHCsandNHCsexhibitaffinities

tomouse2ARthatarecomparablewiththoseseenin

otherexperimentalmodels.Whenassayedbydisplace-

mentof[3H]ketanserinfrommembranespreparedfrom

mousecortex(seeFigureS1intheSupplementalData),

allagonistsdisplayedaffinitiesthatwereconsistentwith

ratandhumanvalues(Hoyeretal.,1994).Thus,the2AR

signalingsysteminmicepresentsatractablemodel

systemtostudytheeffectsofHCs.

AcuteBehavioralResponsesInducedbyHCs

Behavioralanimalmodelscannotcapturetheperturba-

tionsofperception,cognition,andmoodproducedby

HCsinhumans.However,rodentsmightexhibitbehav-

ioralproxiesofhumanhallucinogeniceffects.Systemic

administrationofHCsinratsandnonhumanprimates

elicitsseveralunconditionedeffects:changesinexplor-

atorybehavior(AdamsandGeyer,1985a),grooming

(TrulsonandHowell,1984),interruptionofoperantre-

sponding(MoklerandRech,1984),headtwitchresponse

(HTR),earscratchresponse(ESR),andhyperthermia

(CorneandPickering,1967;Darmanietal.,1990;Maj

etal.,1977;SilvaandCalil,1975).

Toidentifyamousemodelofacutehallucinogenicpo-

tential,weexaminedavarietyofresponsesproducedby

severalHCsandNHCs(FigureS2).Amongthebehavioral

measuresassayed,onlytwowereelicitedbyHCsand

notNHCs:theESRandHTR.Othermeasuressuchasloco-

motion,rearing,grooming,andbasalbodytemperature

changeswereinconsistentlyaffectedbyHCsandNHCs

(FigureS2andTablesS1andS2intheSupplementalData).

TheHTRandESRwerebothdependentuponthepres-

enceof2ARsignalingcapacity,evenatahighdoseofDOI

(FigureS2).However,theESRwasnotelicitedbyevery

HCandwasnotnormallydistributedamongindividual

mice—provingtobean‘‘allornothing’’response.Incon-

trast,HTRwasreliablyandrobustlyelicitedbyallHCs

tested.Furthermore,HTRwasnotproducedbyNHCs,

andwasabsentinhtr2AÀ/Àmice.

All2ARagonistsstudied[DOI,1-(2,5-dimethoxy-

4-methylphenyl)-2-aminopropane(DOM),1-(2,5-dimethoxy-

4-bromophenyl)-2-aminopropaneDOB(DOB),psilocin,

mescaline,LSD,ergotamine,R-lisuride,andS-lisuride]penetratetheCNSaftersystemicadministration.How-

ever,onlythedrugswithhallucinogenicpotentialin

humans(Nichols,2004)activatedasignificantHTRin

htr2A+/+mice,butnotinhtr2AÀ/Àmice(Figure1A).The

NHC2ARagonists(ergotamine,R-lisuride,andS-lisuride)

wereinactiveinbothgenotypes(Figure1A).Thus,the

HTRwasusedasamousebehavioralproxyofhuman

hallucinogenicpotentialinsubsequentstudies.

HCsElicita2ARSignalingResponseDistinct

fromNHCs

Consistentwithpsychoactiveeffectsofcertain2AR

agonistsinhumans,theHTRwasproducedonlybythe

HCs,asubsetofdrugswith2ARagonistproperties.To

explainthisfinding,wereasonedthatHCsmightinteract

with2ARtorecruitspecificsignalingpathwaysnot

activatedbyNHCs.

Totestthishypothesis,wecomparedHC-andNHC-

activationofmultiplesignaltransductionpathways.Be-

causesignaltransductioncascadesultimatelyregulate

genetranscription(RufandSealfon,2004),weassessed

HCandNHCsignalingbymeasuringthe‘‘downstream’’

transcriptomeresponseselicitedbyHCsandNHCsin

mouseSSC,aresponsiveandreliabletissueforassessing

thecellularresponsesofHCs(Gonzalez-Maesoetal.,

2003;Scruggsetal.,2000).Wequantifiedtheinvivoin-

ductionof19transcriptsregulatedbyHCsandNHCsin

htr2A+/+andhtr2AÀ/Àmice(TablesS3andS4).Eachago-

nistelicitedadifferentialandreproducibleresponse.To

assessthepredictivevalueofthesegeneinductionre-

sponsesonbehavior,weusedprincipalcomponentsanal-

ysis(PCA)toreducea19-dimensionalsignalingspace

(reflectedbygenetranscripts)totwoaxes(Figure1B).

Plottedinthisway,thetranscriptomeresponsesofHCs

andNHCspredictedtheirbehavioraleffectsinhtr2A+/+

andhtr2AÀ/Àmiceandtheirhallucinogenicpotentialin

human(Figure1B).Weselectedthemostinformative

signalingresponsemarkersfordistinguishing2ARactiva-

tion,aswellasHCfromNHCbystatisticalsignificance

(TablesS5andS6).Regulationofc-fostrackedwithago-

nistactivityat2AR,andinductionofegr-2andegr-1

mostrobustlypredictedbehavioralactivityofHCsin

mouse(Figure1CandTablesS7andS8).

ActivationofTranscriptomeResponseinNeurons

thatExpress2AR

TheeffectsofHCsandNHCsontranscriptomeactivation

indicatedthatthesecompoundsinteractwith2ARto

activatedistinctsignalingpathways.Thisinterpretation

impliesthatthegenesinducedbyHCsandNHCsshould

beregulatedinneuronsexpressing2AR.Totestthisidea,

wepreparedprimaryculturesofcorticalneuronsfrom

htr2A+/+andhtr2AÀ/Àmouseembryos.Usingfluorescent

insituhybridization(FISH),wefoundthatbothLSDand

R-lisurideinducedc-fosexpressioninneuronsexpressing

2ARmRNA,whileonlyLSD(butnotR-lisuride)induced

egr-2expressionin2AR-expressingneurons(Figures2A

and2B).FISHstudiesofprimaryculturesderived

from

440Neuron53,439–452,February1,2007ª2007ElsevierInc.Neuron

HallucinogenSignallinginCorticalNeurons