ABSTRACT Introduction: Aimrepositorium.sdum.uminho.pt/bitstream/1822/18737/3...Acute antenatal DEX...
Transcript of ABSTRACT Introduction: Aimrepositorium.sdum.uminho.pt/bitstream/1822/18737/3...Acute antenatal DEX...
ABSTRACT
Introduction:Brainregionsimplicatedinsexualbehaviorbegintodifferentiateinthelast
trimesterofgestation.Antenataltherapywithcorticosteroidsisoftenusedinclinicalpractice
duringthisperiodtoacceleratelungmaturationinpre‐termriskpregnancies.Clinicaland
animalstudieshighlightedmajorbehavioralimpairmentsinducedlaterinlifebythese
treatments,especiallywhensyntheticcorticosteroidsareused.
Aim:Toevaluatetheimplicationsofacuteprenataltreatmentwithnaturalversussynthetic
corticosteroidsonadultmaleratsexualbehavioranditsneurochemicalcorrelates.
Methods:TwelvepregnantWistarratswereinjectedwithdexamethasone(DEX‐1mg/kg),
corticosterone(CORT‐25mg/kg)orsalineonlategestation(pregnancydays18and19).
Followingthisbriefexposuretocorticosteroids,weassessedthesexualbehavioroftheadult
maleprogenyandsubsequentlycorrelatedthesebehaviorswiththelevelsofcathecolamines
andmRNAofdopamineandandrogenreceptors(AR)inbrainregionsrelevantforsexual
behavior.
MainOutcomeMeasures:Sexualbehaviorofadultmaleoffspringwasassessedbyexposureto
receptivefemales.Thiswascorrelatedwithserumtestosteronelevelsandlevelsof
cathecolamines(determinedbyHPLC)anddopamineandandrogenreceptorsmRNAexpression
(real‐timePCR)inbrainregionsimplicatedinsexualbehavior.
Results:PrenatalDEXexposureresultedinadecreasednumberandincreasedlatencytimeto
mountsandintromissionsinadulthood.Thesefindingscorrelatedwithdecreasedlevelsof
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serumtestosteroneandincreasedhypothalamicexpressionofARmRNA.DEXanimalsalso
displayedlowerdopaminelevelsandhigherdopaminereceptormRNAexpressionbothin
hypothalamusandnucleusaccumbens(NAcc).ThemilderphenotypeofCORTanimalswas
correlatedonlywithdecreaseddopaminelevelsinNAcc.
Conclusion:Antenatalcorticotherapyprogramsadultmalesexualbehaviorthroughchangesin
specificneuronalandendocrinemediators.Importantly,equipotentdosesofcorticosterone
triggerlessdetrimentalconsequencesthandexamethasone,emphasizingthedifferentialimpact
ofactivationofthedifferentcorticosteroidreceptors.
Keywords:Antenatalcorticotherapy;Corticosteroids;Dopamine;Neurodevelopment;Sexual
behavior
Wordcountoftext(includingabstract):2494
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INTRODUCTION
Thelasttrimesterofgestationandearlypostnatalperiodarecriticalforbrainsexual
differentiation(Segarraetal.,1991).Insultsatthisperiod,includingstressandprolonged
exposuretocorticosteroids,havebeenshowntodisruptseveralbehaviorsinadulthood,namely
malesexualbehavior(Holsonetal.,1995,Gerardinetal.,2005,Pifferetal.,2009).Interestingly,
exposuretocorticosteroidsduringlategestationhasbeencorrelatedwithasustained
perturbationinmalesteroidogenesis(Pageetal.,2001)andanimpoverisheddopaminergic
innervationofthenucleusaccumbens(NAcc)(Leaoetal.,2007),whichisofparticularrelevance
whenconsideringthefacilitatoryroleofdopamineinthedifferentaspectsofsexualbehavior
(GiulianoandAllard,2001).
Inclinicalpractice,glucocorticoidsareprescribedinabout10%ofpregnanciesatriskofpreterm
deliveryinordertopromotefetallungmaturation(Crowley,1995,NIH,1995,Craneetal.,
2003).Dexamethasone(DEX)andbetamethasone,thepreferreddrugs(Jobeetal.,2003),are
syntheticcorticosteroidsthatcrosstheplacentawith100%efficacyandhavebeenshownto
reducethemorbidityandmortalityofthepreterminfantafterdelivery(NIH,1995).Despite
this,thesafetyoftheexposureofthedevelopingfetalbraintoglucocorticoidshasbeen
questionedasitmighthavelife‐longeffectsonadultbehaviorandneuroendocrinefunction
(Matthews,2000,Welbergetal.,2001,Oliveiraetal.,2006).Availabledatasuggeststhatthe
activityofthehypothalamic‐pituitary‐adrenal(HPA)axis,whichisvitaltostressresponse,might
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bereprogrammedbymanipulationsinthecorticosteroidmilieuduringlategestation;this
alteredpatternoftheHPAisbelievedtobe,atleastinpart,responsibleforthebehavioraland
neuroendocrinechanges(WelbergandSeckl,2001),aswellasforincreasedriskfor
hypertension,type2diabetes(Levittetal.,1996,Lindsayetal.,1996,Sapolskyetal.,2000)and
neuropsychiatricdisorders(Welbergetal.,2001).Ofparticularinterestistheevidence
suggestingalessdeleteriouseffectonadultemotionalbehavioroftheacuteadministrationof
endogenouscorticosteroids(Oliveiraetal.,2006),especiallyinlightofevidenceshowingthat
cortisoldisplayssimilartherapeuticefficacytoDEXduringpregnancyandneonatallife(Crowley,
1995).
Inlightofthisevidence,wedecidedtoassesstheimpactofshort‐termantenatalcorticosteroid
exposureinmalesexualbehaviorandsearchforitsneurochemicalandendocrinecorrelates.
Furthermore,wealsowantedtocomparenaturalandsyntheticcorticosteroidsintermsoflong‐
termadverseeffects.
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METHODS
Animalsandtreatments
Experimentswereconductedinaccordancewithlocalregulations(EuropeanUnionDirective
86⁄609⁄EEC)andNIHguidelinesonanimalcareandexperimentation.
TwelveadulttimedpregnantWistarHanrats(Charles‐RiverLaboratories,Barcelona,Spain)
receivedatday14ofgestationwereindividuallyhousedunderstandardlaboratoryconditions
(12/12hlight/darkcycle,withlightsonat8a.m.;foodandwateradlibitum).
SubcutaneousinjectionsofDEX(1mg/kg,Sigma‐Aldrich;n=4),corticosterone(CORT,25mg/kg,
Sigma‐Aldrich;n=4),orsaline(controls,1mL/kg;n=4)wereadministeredonembryonicdays
(ED)18and19ofpregnancy(Oliveiraetal.,2006).Drugdosageswerechosentoachieve
comparabletransrepressivepotenciesattheglucocorticoidreceptors(GR)(SchimmerBP,2005).
Weaningwasperformedatpostnatalday21andpupswerepair‐housedaccordingtogender
andprenatalexposure.Maleoffspring(2siblingsperdam;n=4dams/group),weretestedat3
monthsforsexualbehavior.
Preparationofsexuallyreceptivefemales
Adult3monthsfemaleratswereindividuallyhousedandovariectomized,aspreviously
described(Agmo,1997).Sexualreceptivitywasinducedbysubcutaneousestradiolbenzoate(20
µg/rat,SigmaAldrich)andprogesterone(1mg/rat,Sigma‐Aldrich)52and4hoursbeforemale
exposure,respectively.
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Malesexualbehavior
ThetestarenaconsistedofarectangularPlexiglasbox(40x60x40cm)withatransparenttopand
avideocameraoverit.Exposurewasconductedtwohoursaftertheonsetofthedarkphase,in
aquietroom,withadimredlight.Sexuallyexperiencedmaleswereplacedinthearenaten
minutesbeforeareceptivefemalewaspresentedandactivitywasrecordedfor20minutes;
latencytimeandnumberofmountsandintromissions(vaginalpenetration)wereregistered
andintromissionratiocalculatedasintromissions/[intromissions+mounts].
Biometricandtestosteronemeasurements
Animalsweresacrificedoneweekafterbehaviorassessmentandbloodcollectedfor
determinationofserumtotaltestosteronelevelsbyelectrochemiluminescenseimmunoassay
(ElecsysTestosteroneIIreagentkit,RocheDiagnostics;measuringrange2.5‐1500ng/dL).Testis
wetweightwasassessed.
Braincathecolamines
Afterbrainsnapfreezing,theregionsofinterestwererapidlydissectedunderthescopeusing
macrodissectionofspecificbrainareas.Thehypothalamuswasisolatedbyplacingwholebrains
upsidedownandusingdelicateforceps(Dumont#7forceps,FineScienceToolsUSAInc.,Foster
City,CA,USA)todetachitfromtherest.Thehypothalamuswasidentifiedastheroundshaped
areainthecenterofthebrain.NAccwasisolatedusingpunchdissectionin2mmsectionsof
brains(AltoTMbrainmatrix,StoetlingCo.,WoodDale,IL,USA)andidentifiedundera
stereomicroscope(ModelSZX7,OlympusAmericaInc.,CenterValley,PA,USA).NAccwas
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identifiedasthetissueinthevicinityoftheanteriorbranchoftheanteriorcommissure,
accordingtoPaxinosstereologicalcoordinates(PaxinosandWatson,2005).Sampleswere
frozeninliquidnitrogen(overnightat‐20ºC)afteraddingpercloricacid0.2M.Sampleswere
brieflysonicated,centrifugedand50µlaliquotsofthesupernatantinjectedonahigh
performanceliquidchromatography(HPLC)combinedwithelectrochemicaldetectionsystem.A
mobilephaseof0.7Maqueouspotassiumphosphate(monobasic)(pH3.0)in10%methanol,1‐
heptanesulfonicacid(222mg/l)andNa‐EDTA(40mg/l)wasused.
Levelsof5‐HT,5‐hydroxyindoleaceticacid(5‐HIAA),dopamine,3,4‐dihydroxyphenylaceticacid
(DOPAC)and4‐hydroxy‐3‐methoxyphenylaceticacid(homovanillicacid,HVA)weredetermined
usingaGilsoninstrument(GilsonInc.,Middleton,WI,USA),fittedwithananalyticalcolumn
(SupelcoSupelcosilLC‐183M;7.5cmx4.6mm;flowrate:1.0–1.5ml/min;Supelco,Bellefonte,
PA,USA).Astandardcurvewasthenobtainedanddatapresentedasconcentration(nanogram
permilligramoftissueprotein).
Molecularanalysis
ForReal‐TimePCRanalysis,totalRNAwasisolatedfromfrozenareasusingTrizol(Invitrogen)
andDNasetreatment(Fermentas),accordingtomanufacturer.TwoµgofRNAwereconverted
intocDNAusingtheiSCRIPTkit(Biorad).RT‐PCRwasperformedusingSyberGreen(Qiagen)and
theBioradq‐PCRCFX96apparatus.HPRTwasusedasahousekeepinggene.Weusedrelative
quantificationtodeterminethefoldchangedifferencebetweencontrol,CORTandDEXanimals,
usingtheΔΔCTmethodasdescribedbefore(Pfaffl,2001).Primersequenceswere
AR_F:GGGTGACTTCTCTGCCTCTG,AR_R:CCACAGATCAGGCAGGTCTT(androgenreceptor);
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ESR1_F:CAGGTGCCCTACTACCTGGA,ESR1_R:GGTAGCCAGAGGCATAGTCG(estrogenreceptor1);
ESR2_F:AACCGCCATGAGTATTCAGC,ESR2_R:GTAACAGGGCTGGCACAACT(estrogenreceptor2);
nNOS_F:GACAACGTTCCTGTGGTCCT,nNOS_R:GAAGAGCTGGTCCTTTGTGC(neuronalnitricoxide
synthase);D1R_F:TCCTTCAAGAGGGAGACGAA,D1R_R:CCACACAAACACATCGAAGG(dopamine
D1receptor);D2R_F:CATTGTCTGGGTCCTGTCCT,D2R_R:GACCAGCAGAGTGACGATGA(dopamine
D2receptor);HPRT1_F:GCAGACTTTGCTTTCCTTGG,HPRT1_R:TCCACTTTCGCTGATGACAC.
Statisticalanalysis
Forstatisticalanalysis,the“n”ofeachexperimentgroupwasconsideredthenumberoflitters
fromwhichindividualswerederived.Resultsarepresentedasaverage±SE.Datawasanalyzed
byPASWStatistics18.0(SPSSInc,Chicago,IL,USA),usingANOVA.Wheneverappropriate,post
hoccomparisonswereperformedusingTukeytest;statisticalsignificancewasconsideredwhen
p<.05.
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RESULTS
AcuteantenatalDEXexposureaffectsadultmalesexualbehavior
Treatmentsignificantlyaffectedsexualmotivationandthevolitiveaspectsofcopulatory
behavior(F=20.057,p<.001),asrevealedbyanincreasedlatencytomountinDEX‐exposed
animalscomparedtocontrols(p<.001)andCORTsubjects(p=.029),respectively(Figure1).
CORTanimalswerealsodifferentfromcontrols(p=.027).
Treatmentalsoaffectedthenumberofmounts(F=5.233,p=.031),anothermeasureofsexual
motivation(Agmo,1997),whichwassignificantlydecreasedinDEX‐exposedsubjectswhen
comparedtocontrols(p=.027).Interestingly,CORTratswerenotdifferentfromtheother
groups.
Incontrasttomounts,intromissionsarenotexclusivelydependentonsexualmotivation.
Treatmentaffectedthisparameter(F=23.081,p<.001)asrevealedbyanincreasedlatencyof
DEXprogenyincomparisontocontrols(p<.001)andCORTsubjects(p=.016).Again,CORT
animalsalsotookmoretimetointromissionthancontrols(p=.024).
Moreover,thenumberofintromissionswasaffectedbytreatment(F=8.083,p=.010).This
indicatoroftheeasinessintheactivationofejaculatoryreflexes(Agmo,1997)wasfoundtobe
decreasedinDEX‐exposed(p=.008),butnotonCORT‐exposedsubjects(p=.103).
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Intromissionratio(Figure2),anindicatorofefficiencyofpenileerection,wasalsoaffectedby
treatment(F=22.972,p<.001).DEX‐subjectsdisplayedsignificantlylowerratioscomparedto
controls(p<.001)andCORT‐exposedanimals(p=.003).
AdulttestosteronelevelsareaffectedbyantenatalDEX
SerumtestosteronelevelsweresignificantlyreducedbyantenatalDEXexposure(F=15.815,
p=.001;vsCORTp=.001;vscontrolsp=.004)butnotbyCORT(Figure3).Testiswetweightwas
similarbetweengroups(datanotshown).
Antenatalcorticosteroidsinfluencebraindopaminelevels
AntenatalcorticosteroidsexposureinfluencedthelevelsofdopamineinNAcc(F=39.911,
p<.001;Table1).BothprogenyofCORTandDEXdamsdisplayeddecreasedlevelsofdopamine
inNAccincomparisontocontrols(p<.001andp<.001,respectively).Treatmentalsoaffected
dopamineturnover(F=6.162,p=.021),withanincreaseinDEXsubjectswhencomparedtoCORT
(p=.026)andcontrols(p=.047).
Hypothalamiclevelsofdopaminewerealsosignificantlyaffectedbyantenataltreatment
(F=5.817,p=.024),withadecreaseonlyinDEX‐treatedsubjects(p=.022)whencomparedto
controls.Dopamineturnoverinthisareawasalsoaffected(F=10.286,p=.005),withCORTand
DEXanimalsdisplayingalowerratiowhencomparedtocontrols(p=.010and.008,respectively).
Treatmentdidnotaffectserotoninlevels(F=3.564,p=.072)noritsturnover(F=1.076,p=.381)in
theNAcc.However,hypothalamiclevelsofserotoninwerereduced(F=14.050,p=.002)whileits
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turnoverwasincreased(F=7.552,p=.012)inbothDEX(p=.003;p=.029)andCORT(p=.004;
p=.016)groups.
Molecularcorrelates
IntheNAcc,dopamineD1(D1R)andD2(D2R)receptorsmRNAlevelsweresignificantlyaffected
byprenatalexposuretocorticosteroids(F=111,471,p<.001andF=76.383,p<.001,respectively;
Table2),withanincreaseinDEXgroupwhencomparedtocontrols(p<.001;p<.001,
respectively)andCORT(p<.001;p<.001,respectively).Asimilareffectwasalsoobservedinthe
hypothalamus,butonlyforD1R(F=7.868,p=.011;vscontrolsp=.009);CORTanimalswerenot
differentfromanyothergroup.
LevelsofARandneuronalnitricoxidesynthase(nNOS)mRNAwerenotdifferentbetween
groupsintheNAcc.However,inhypothalamus,therewasasignificanteffectofexposureonAR
(F=13.049,p=.002)andnNOS(F=27.056,p<.001)mRNAlevels,withanincreaseinDEXprogeny
whencomparedtocontrols(p=..020;p<.001,respectively)andCORTsubjects(p=.002;p=.002,
respectively).
Levelsofestrogenreceptors1and2werenotaffectedbytreatmentinneitherarea.
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DISCUSSION
Inrats,brainsexualdifferentiationoccursmainlyduringlategestation(ED14–21)andthefirst2
weeksofpostnatallife(Segarraetal.,1991).Thevulnerabilityofthistime‐windowtoseveral
insults,includingstressandcorticosteroidexposure,maythusleadtolong‐termconsequences
onadultmalesexualbehavior(Gerardinetal.,2005,Pifferetal.,2009).Infact,previousdata
suggeststhatprenatalstressdisruptsthenormalmaternalhormonalmilieuandsuppressesthe
fetaltestosteronepeakonED18and19,requiredforlaterexpressionandmaintenanceofmale
sexualbehavior(WardandWeisz,1984,Lalauetal.,1990).Suchdatasustainthatinterferences
inthematurationofthehypothalamic‐pituitary‐adrenal(HPA)axis,affectthehypothalamic‐
pituitary‐gonadal(HPG)axis,sincebothareregulatedbycommonplayersbothcentrallyandat
theperiphery(Pageetal.,2001).Followingtheinitialexperimentalevidenceshowingthatlate
gestationwhole‐bodyrestraintunderbrightlightsresultsindelayedinitiationofcopulation
(WARD1972),morerecentdatacorrelatedprolongedprenatalstress/corticosteroidswith
impairedadultmalesexualbehaviorandreducedserumtestosteronelevels(Gerardinetal.,
2005,Pifferetal.,2009).However,nopreviousstudiesfocusedonthepotentialeffectsofa
short‐termexposurewhichbettermimicstheeverydayclinicalpractice,norinthecomparison
betweendifferenttypesofcorticosteroids.
Theanalysisofseveralbehavioralparameterspermittedustodistinguishbetweenappetitive
andconsummatorycomponentsofmaleratsexualbehavior.Maleratsexualbehavioris
characterizedbyaseriesofmounts,eitherwithorwithoutvaginalpenetration(intromission),
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ultimatelyleadingtoejaculation(HullandDominguez,2007).Whilelatencyuntilthefirstmount
reflectssomeoftheappetitiveaspectsandsexualmotivation,intromissionandejaculation
latenciesbutalsomountandintromissionfrequenciesreproduceconsummatorycomponents
ofcopulatorybehavior(Pfausetal.,1990b,Agmo,1999).Interestingly,theimpairmentofmale
sexualbehaviorobservedinthisstudywasmainlycharacterizedbyalterationsinsexual
appetite(increaseinmountandintromissionlatencies);moreover,thereducednumberof
mountsmightreflectdecreasedsexualmotivation(Agmo,1997).Importantly,thesedifferences
aremorestrikinginanimalsexposedtoDEXthantoCORT.
Regardingtheneurobiologyofsexualbehavior,threemajorintegrativesystemsregulatesexual
motivationandgenitalandmotorresponses(Hulletal.,2004).Whereasthemesolimbicsystem
iscriticalforappetitivebehaviorandreinforcement,themedialpreopticsystemcontributesto
genitalreflexes,sexualmotivationandmotorpatternsofcopulation.Finally,thenigrostriatal
systemenhancesthemotoricreadinesstorespondtostimuli.Dopamineisthecommonkey
playerinallthreesystems,easingsexualmotivation,copulatoryproficiency,andgenitalreflexes
(GiulianoandAllard,2001).Thepathwaysforsexualexcitationinvolvetheactivationof
incertohypothalamicandmesolimbicdopaminetransmissionthattargetsthehypothalamic
medialpreopticarea(MPOA)andNAcc,respectively(Pfaus,2009).Asaresult,inthemalerat
thereisaslightincreaseindopaminereleaseinNAccfollowingpresentationtoareceptive
femalethatisfollowedbyasharpincreaseindopaminetransmissionduringcopulation,that
graduallydeclinesaftertheremovalofthefemale(Pfausetal.,1990a).
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Apreviousstudyfocusingontheeffectsofprolongedprenatalimmobilizationstressonthe
adultmaleratcorrelatedtheabsenceofcopulatorybehaviorswithunchangedNAcc
extracellularlevelsofdopamine,DOPACandHVAduringexposuretoreceptivefemales.Such
data,obtainedthroughsimultaneoussexualbehaviortestingandconcomitantmicrodialysis
samplig,suggestedthatintenseenvironmentalstressorsmightimpairNAccdopaminerelease
(WANG1995).
Inourexperiment,aninterestingneurochemical‐behaviorcorrelatewasestablished,aswe
founddecreaseddopamineinhypothalamusandNAccofcorticosteroidbrieflyexposed
animals.Interestingly,wehadpreviouslyreportedareduceddopaminergicinnervationofthe
NAccfollowingprenatalshort‐termexposuretoDEX,revealedbyareduceddensityoftyrosine
hydroxylase‐positivefibersinthesesubjects(Leaoetal.,2007).Inaddition,thedecreasein
dopaminelevelsinNAcchereinreportedislikelytobeofrelevanceforthechangesinsexual
behaviorifonetakesintoaccountdescriptionscorrelatingadelayedonsetofcopulationand
ejaculationwithadiminishedreleaseofthisneurotransmitterinthemesolimbictract(Hullet
al.,2004).Furthermore,theincreaseindopamineD1andD2receptorsmRNAintheNAcc
followingDEXexposurehereinshownfurthersupportstheexistenceofahypodopaminergic
statusintheseanimals,andmayappearasacompensatorymechanismduetothelow
dopaminelevelsobserved.
AlthoughweobservedsubstantialdifferencesinthedopaminelevelsandreceptorsintheNAcc,
onedrawbackofthisworkisthefactthatwedidnotdiscriminatebetweenitstwofunctionally
distinctregions:thecoreandtheshell.C‐fosexpressionisincreasedinthecorebutnottheshell
duringsexualbehavior(BradleyandMeisel,2001).Onthecontrary,administrationofdrugsof
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abuseresultsinincreaseddopaminelevelsintheshelloftheNAcc(Pontierietal.,1995,Nisell
etal.,1997,DiChiaraetal.,1999)(DICHIARA2002).Thissuggeststhatshellandcoremightbe
activateddifferentlyinresponsetonaturalreinforcersanddrugsofabuse.Indeed,NAcc
neuronsexhibitsimilarneuronalactivityduringrespondingtotwonaturalrewards‐foodand
water,butdifferentfiringpatternsduringrespondingforanaturalrewardversuscocaine(Carelli
etal.,2000).Therefore,consideringthedifferentfunctional/activationalrolesofcoreandshell,
itwouldbeinterestingtoanalyzedopaminemetabolismandreceptorsineachsubareainorder
todissectwhatisthemostaffectedarea.
ThehypodopaminergicstatusofDEX‐exposedanimalsintheNAccmighthaveotherbehavioral
consequencesbesidesalteredsexualbehavior,consideringtheimportanceofcorrectdopamine
inputforfeeding,rewardandaddiction,amongothers.DopamineisreleasedintheNAccin
responsetodrugsofabusebutalsootherconsumatorybehaviorssuchassexandfoodandthus
theVTA‐NAccpathwayisalsoknownasthe“rewardpathway”(PiazzaandLeMoal,1996).
Interestingly,somestudieshavereportedcross‐sensitizationbetweenrepeatedexposuresto
pharmacologicalagentsandnaturalmotivatedbehaviorssuchassex(MitchellandStewart,
1990a,b,FiorinoandPhillips,1999).Forexample,sexualexperiencecancross‐sensitize
neuronalresponsestoamphetamineandthisseemstodependondopaminereleaseinthe
NAcc(BradleyandMeisel,2001).
Theintricately‐regulatedbalancebetweenhypo‐andhyper‐dopaminergicstatesinthe
mesolimbiccircuit,speciallyintheNAccarea,underliesanindividual’scyclesofdrug‐seeking
behavior/abuseandresponsetonaturalrewards.Whileahyperdopaminergicstateseemsto
enhancethemotivationalorrewardingpropertiesofdrugsofabuse,hypodopaminergicstates
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appeartoenhancedrug‐seekingbehaviorinparallelwithreductionsintheperceived
motivationalimpactof‘natural’rewardssuchasfoodandsex(Dianaetal.,1993,Dianaetal.,
1998,Melisetal.,2005).Thistheoryisinagreementwithourbehaviouralandneurochemical
results,giventhefactthatDEX‐animalshavelowdopaminelevelsintheNAccand,
concomitantly,impairedappetitivesexualbehaviour.Additionally,itsuggeststhatthese
animalsmightalsodisplaydifferentialsusceptibilitytoaddiction,aphenomenonalsoobserved
inothermodelsofearlylifestress(Kippinetal.,2008).
Dopamineinthehypothalamus,particularlyintheMPOA,isessentialforgenitalreflexes,motor
patternsofcopulation,andprobablysexualmotivation(HullandDominguez,2006);several
studiesdescribedthefacilitativeroleofincreasedlevelsintheMPOAonsexualbehavior,
suggestingthattestosteronemightmediatethiseffect(DOMINGUEZ2005).Inthepresent
study,conclusionsontheimpactofprenatalexposuretonaturalversussynthetic
corticosteroidsarelimitedbythefactthatdissectionofthewholehypothalamicareawas
performedinsteadofisolatingtheMPOA.Nonetheless,thedecreasedhypothalamiclevelsof
dopaminehereinreportedintheDEXgroup,butnotintheCORTgroup,isassociatedwitha
significanteffectonD1receptorsmRNA.Thisfactislikelytobeofsignificancetoexplainthe
differentialneuroendocrineandbehavioraleffectsofCORTfromDEX.
Inaddition,anincreaseintheandrogenreceptormRNAwasobservedinthehypothalamusof
DEXprogeny,possiblyreflectingareductioninthecirculatingandrogens.Interestingly,previous
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studiesshowedthatalthoughnormalbasallevelsofdopamineintheMPOAareadequateto
allowsomecopulatorybehavior,efficientmatingrequiresanandrogen‐dependentfemale‐
stimulatedincrease(Putnametal.,2005).Also,byup‐regulatingnNOSintheMPOA,
testosteroneenhancesnitricoxideproduction,whichcontrolsdopaminerelease(Sandersonet
al.,2008).Inthepresentstudy,wefoundincreasedlevelsofnNOSmRNAinthehypothalamus
ofDEXsubjects.ItwouldbeofaddedvaluetoassessiftheseschangespersistinMPOAsamples,
whichwouldbeinaccordancetopreviousdescriptionsintheMPOAofgonadectomizedrats
(Singhetal.,2000).However,technicalissuesintheisolationoftheMPOAandthefactthat
neighborhypothalamicsubareasmightdisplaydifferentsusceptibilitiestocirculatingandrogens
couldjustifywhyotherstudiesdidnotconfirmtheoriginalfindings(Satoetal.,2005).
Thus,inordertodrawfurtherconclusionsontheimpactoftheinuterocorticosteroids
exposureontheadultmaleMPOA,itwouldbeofinteresttospecificallyanalyzethis
hypothalamicareainfuturestudies.
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CONCLUSIONS
Earlylifeexposuretoshort‐termglucocorticoidligandstriggerslifelongprogrammingeffectsin
brainregionsimplicatedindistinctaspectsofmalesexualbehavior.Thebehavioralchanges
correlatewithaltereddopaminergicsystemsandneuroendocrinemarkers.Thesefindingsareof
clinicalrelevance,astheyprovidesupporttotherapeuticinterventionsforsexualdysfunction
thatmodulatebraindopaminergiclevels(Montorsietal.,2003a,Montorsietal.,2003b,Padma‐
Nathanetal.,2004,MinerandSeftel,2007)andperipherallevelsoftestosterone
(HatzimouratidisandHatzichristou,2007,Traishetal.,2007,Hatzimouratidisetal.,2010).
Noticeably,equipotentCORTadministrationtriggersalessdetrimentalimpairmentthanDEX,
highlightingtheroleofthedifferentcorticosteroidreceptorsonthesystemsregulatingsexual
behavior.
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FIGURELEGENDS
Figure1–Latencytimestomountandintromissionwereincreasedindexamethasone(DEX)
andcorticosterone(CORT)exposedanimalswhencomparedtocontrols(left);thenumberof
mountsandintromissionswassignificantlyreducedinDEX‐exposedrats(right).*p<.05.
Figure2–Intromissionratio,calculatedasintromissions/[intromissions+mounts],was
diminishedinDEX‐exposedratswhencomparedtocontrolsandCORTanimals.*p<.05.
Figure3–AntenatalDEXadministrationledtodiminishedserumtestosteronelevels(ng/dL)in
adultmalerats,whencomparedtoCORTandcontrols.*p<.05.
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