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Electric

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Electric

    Electric

    NEULREGENERATIONRESEARCH

    Volume2,Issue7,July2007

    Availableonlineat

    ':;,ScienceDirect

    ,^,,fI,,?.sciencedirect.corn

    Electricstimulationatsciaticnerveevokeslong-term

    potentiationofcornudorsalemedullaespinallsfield

    atvariousdevelopmentalphases?

    JiangWu,DanShu,QishengHu

    DepartmentofPhysiology,MedicalCollegeofWuhanUniversity,Wuhan430071,HubeiProvince,China

    Abstract

    BACKGRoUND:Long

    termpotentiationofcornudorsalemedullaespinalisfieldpotentialinaduItratshas alreadybeenreported;however.thereislackofcorrelatedresearchesonnaenonate,infantandadultrats

    whichhavedifierentresponsestopainconductioninformation.

    oBJECT?E:Toobservethevariouseffectsofelectricstimulationatsciaticnerveonlong

    term

    potentiationofevokedfieldpotentialatsuperficiallayerofcomudorsalemedullaespinalisofratsatvarious

    developmentalphasesandanalyzemanifestationsofpainconductioninformationatsuperficiallayers(III)

    ofcomudorsalemedullaespinalisinimmaturerats.

    DESIGN:GroupingcontrolledstudV.

    SETTING:DepartmentofPhysiology,MedicalCollegeofWuhanUniversity.

    MATERIALS:TheexperimentwascarriedoutintheLaboratoryofPhysiology(provinciallaboratory),

    MedicalCollegeofWuhanUniversityfromMarch2006toMav2007.Atotalof27healthymale

    Sprague-Dawley(SD)rats,1790daysold,SPFgrade,weighing41

    200g,wereprovidedby

    ExperimentalAnimalCenter,MedicalCollegeofWuhanUniversity.

    MTH0DS:Basedontheirbirthdays,ratsweredividedintonaenonategroup(17

    20daysold,weighing

    4l52g,"=l0),infantgroup(3550daysold,weighing87125g,"10)andadultgroup(60

    90days

    old'weighingl80

    200g,"=71.Leflsciaticnervewasseparatedandstimulatedwithsinglesquarewave (15V,0.5ms).Meanwhile,evokedfieldpotentialwasrecordedatsuperficiallayersoflateralT3Lcomu

    dorsalemedullaespinalisandthenstimulatedwithhighfrequentandhigh

    intensivetetanizingcurrent(30

    40v'0.5ms,lo0Hz,lsperbundle,l0sinbundleinterva1)fourtimes.Aflertheoperation,onsetoflong.term

    potentiationwasobserved:meanwhile.amplitudechangesandlatencyoffieldpotentialwereanalyzed.

    MAoUTCoMEMEASURES:Amplitudeandlatencychangesoffieldpotentialatsuperficiallayersof

    comudorsalemedullaespinalisofratsinthethreegroups.

    RESULTS:Atotalof27acceptedratswereinvolvedinthefinalanalysis.)Amplitudechanges:Electric

    stimulationatsciaticnervewithhigllfrequentandhigh

    intensivetetanizingcurrentcouldinduceevoked

    fieldpotentialatsuperficiallayersfI

    II1ofcomudorsalemedullaespinalisinthethreegroups.

    Long..termpotentiationinthenaenonategroupmanifestedthatamplitudeofA..kindneverfiberwasraised

    andtherewassignificantdifference<0.05).Inaddition.averageamplitudewasincreasedandtherewas

    obviouslysignificantdifference<0.0l1.Long

    termpotentiationintheinfantgroupmanifestedthat

    amplitudeofC

    kindneverfiberwasraisedandtherewassignificantdiffefence(P<0.0l1;while,long

    term

    potentiationintheadultgroupmanifestedthatamplitudeofC.kindneverfiberwasraisedandtherewas

    significantdifference(

    <0.O1).otherwise,latenciesinthethreegroupswereallshortened.?Latency

    changes:AveragelatencyofA

    kindnervefiberinthenaenonategroupwasshortenedandtherewas significantdifference(P<0.O1):inaddition,evokedpotentialofC-kindnervefiberwaslowandlatencywas

    immovable.Tllerewasnosignificantdifferencebeforeandafterhigh.frequentandhigh

    intensiveelectric

    stimulation>0.05).AveragelatencyofC

    kindnervefiberintheinfantgroupwasshortenedandthere

    wassignificantdifierence<0.01):inaddition,evokedpotentialofA

    kindnervefiberwasstableand

    latencywasimmovable.Therewasnosignificantdifferencebeforeandafterhigh

    frequentand

    highintensiveelectricstimulation>0.05).AveragelatencyofC

    kindnervefiberintheadultgroupwas

    shortenedandtherewassignificantdifference<0.01):inaddition,evokedpotentialofA

    kindnervefiber

    wasstableandlatencywasiremovable.Therewasnosignificantdiffefencebeforeandafterhi

ghfrequent

    andhigh-intensiveelectricstimulation. C0NCLUSIoN:EvokedfieldpotentialatsuperficiallayerofCOmUdorsalemedullaespinali

    scanbe

    reenrdedthroughelectricstimulationatsciaticnerve.Singlestimulationandtetanizingelectr

    icstimulation

    callcausedifferentcharacteristicsofevokedfieldpotentialinratsatvariousdevelopmentalp

    hases.

    Received:200704-20;Accepted:20070518(07S40434/YWY)

    Correspondingauthor:QishengHu.Professor,DepartmentofPhysiology,MedicalCollege

    ofWuhanUniversity,wuhan

    430071,HubeiProvince,ChinaE-mail:hqs2002@hotmail.corn JiangWu?.Studyingfor

    master'sdegree,Attending

    physician,Departmentof

    Physiology,MedicalCollege

    ofWuhanUniversity,Wuhan

    430071,HubeiProvince.

    China

    WuJ.ShuD.HuQS.Electric

    stimulationatsciaticnerve

    evokeslong-term

    potentiationofcornudorsale

    medullaespinalisfield

    potentialinraIsatvarious

    developmentalphases.

    NeuraIRegenRas

    2007:2(7):385.9

    WaANVsjzsyj.comlJournall

    0707/07437-385.htmI

385

wujetal/NeuralRegenerationResearch2007,2(7159

    SuperficiallayerofcomudorsalemedullaespinalisofnaenonateratsismainlycausedbyA

    kindnervefiber

    whichDarticil:)antsinpainconductionandformationofpainsensitivity;however,thatofinfa

    ntandadultrats

    mainlydependsonCkindnervefiber.

    KeyWords:longtermpotentiation;spinalcord;electricstimulation Itwasbelievedthatlong-termpotentiationwasthe mechanismunderlyinglearningandmemory;however, evokedpotentialofcorlludorsalemedullaespinalismight generatelongtermpotentiationthroughelectricstimulating C-kindfiberofadultrats,naturallynociceptivestimulusor acutenel'veinjury[_.

    Recentresearchesdemonstratethatlongtermpotentiation

    islastingincreaseofsynaptictransmissionefficiency; therefore,long-termpotentiationofC-fiberevokedpotential ofeornudorsalemedullaespinalismayberelatedto sensitizationofcentralnerveandplaysakeyrolein hyperpathia.

    Someresearchesreportthatlongtermpotentiationisan

    eleetrophysiologicalmanifestationofadultrats. Thisstudywasdesignedtoobservethedifferentresponses topainconductioninformationinnaenonateandinfantrats. MatedaIs

    TheexperimentwascarriedoutintheLaboratoryof Physiology(provinciallaboratory),MedicalCollegeof anUniversityfromMarch2006toMay2007.

Atotalof27healthymaleSprague-Dawley(sD)rats,l7

    90daysold,SPFgrade,weighing41200g,wereprovided

    byExperimentalAnimalCenter,MedicalCollegeOfWuhan University[ABSL-3grade,certification:SCXK(e)2003-004]. Basedontheirbirthdays,ratsweredividedintonaenonate group(1720daysold,weighing4152g,v/10),infant

    group(3550daysold,weighing87125g,F/=10)and

    adultgroup(6090daysold,weighingl80200g,g/---7).

    Motho~

    Modelestablishment

    Animalswereintraperitoneallyanesthetizedwithl00g/L urethane(1g/l(g)andperformedwithroutinelyendotracheal intubation.Leflsciaticnervewasseparatedandfixedwith stereotaxieapparatus.Andthen,animalsunderwentT1L1

    lamineetomy.Spinaltissuewaskeptinliquidparaffinat 37?.Next,rats"q/ereintraperitoneallyinjectedwith veeuroniumbromidef0.050.1me,/kg)tomaintainskelaxin

    andbreathingmachineofsmallanimalsWaSusedtomaintain breathinthefrequencyof90l20timesperminute.Stainless

    steelbipolarrecordingelectrodefO.5lMQjnimpedance

    and0.1millintopdiameter)wasinsertedintoleT13L1

    cornudorsalemedullaespinalisandperformedextracellular 386

    recording.Stainlesssteelbipolarexcitingelectrodecrookwas locatedatleftsciaticnerveandliquidparaffinwasusedto protectnerve.Evokedfieldpotentialwasstimulatedbyusing singlesquarewave(15V'0.5ms)for30minutes,

    highfrequentandhigh-intensivetetanizingelectricstimulus (3040V0.5ms,100Hz,lsperbundle,l0sinbundle

    interva1)forfourtimes,andsinglesquarewave(15V'0.5ms)

    f0rmorethan3hours.Changesofamplitudeand1atencyof fieldpotentialwererecordedeveryminute.Amplitudeoffield potentialbuiltuO2530timesin4ratsinthenaenonate

    group,2intheinfantgroupand6intheadultgroup. DeterminationoffieldpotentialevokedbyA-andC-kind fiber

    LatencyevokedbyA.kindnervefiberwasmorethan3ms, andthatevokedbyC.kindnervefiberwasmorethan50ms. Therefore,fieldpotentialevokedbyA.andC.kindfibercould bedetermined.

    Histologicalevaluation

    Atiertheexperiment,Brucebluewasusedtodetecttop sitesofstainlesssteelbipolarrecordingelectrode,l00mL 0.9%NaCland200mLformaldehydesolutioncontaining l00g/L1%ferrocyanatumkaliumwereperfusedintoleft ventricleofanimalstoobtainspinalcord,whichwasstoredat 4?f0roneweekandunderwentparaffinimbedding. sectionsandHEstaining.Topsitesofelectrodewere evaluatedunderopticmicroscopeandthecoincidentdata werecollectedforstatisticaltreatment.

    Statisticalanalysis

    SPSSII.0softwarewasusedbythefirstauthorinthis study.Datawerecomparedwithpairedttestinthesame groupandwithttestinintergroup.Allexperimentaldatawere expressedasMean?SD.

    RESUU

    QuantitativeanalysisoftheexperlmentaIanimals Atotalof27acceptedratswereinvolvedinthefinal analysis.

    Amplitudechanges

    Electronstimulatingsciaticnervewithhigh.frequentand high-intensivetetanizingcurrentcouldinduceevokedfield potentialatsuperficiallayers(1l1)ofCOrnUdorsale

    medullaespinalisinthethreegroups.Long-termpotentiation inthenaenonategroupman~festedthatamplitudeofA.kind neverfiberwasraisedfrom(14.32?1.375)taVtofl8.94?

    2.407)uVwithinthefirst5minutes.andtherewas significantdifference(P<0.05).Inaddition,average

    1.526,taVandthere amplitudewasincreasedas(29.62?

    Wu{etal,/NeuralRegenerationResearch.2007,2(7).'385-9 wasobviouslysignificantdifference(P<0.01,Figure1) Long-termpotentiationintheinfantgroupmanifestedthat amplitudeofC-kindneverfiberwasraisedfromf13.85?

    1.67211/Vto28.43?1.583uVandtherewassignificant

    difference<0.O1,Figure2).

    While,long-termpotentiationjntheadultgroupmanifested thatamplitudeofC.kindneverfiberwasraisedfrom(19.65?

    2.204)Vto(57.89?4.653)uVandtherewassignificant

    difference(P<0.O1,Figure3).

    Incychanges

    AveragelatencyofA.kindnervefiberinthenaenonate groupWaSshortenedfrom(9.32?1.436)msto(7.2l?1.875)

    Illsandel'ewassignificantdifference(P<0.01):inaddition. evokedpotentialofC.kindnervefiberwaslowandlatency wasimmovable.Therewasnosignificantdifferencebefore andafterhigh??frequentandhigh??intensiveelectricstimulation >o.o5).AveragelatencyofCkindnervebetintheinfant

    groupwasshortenedfrom(80.56?1.865)msto(69.6l?

    2.o52)msandtherewassignificantdifference(P<0.0l,

Figure41.

    Inaddition,evokedpotentialofA-kindnervefiberwas stableandlatencywasimmovable.Therewasnosignificant differencebeforeandafterhigh??frequentandhigh?intensive

    electricstimulation(P>0.05,Figure5).

    387

etal/NeuralRegenerationResearch,0D!:

    AveragelatencyofCkindnervefiberintheadultgroup

    wasshortenedfrom(100.28?1.682)msto(68.54+--1.418)ms

    andtherewassignificantdifference(P<O.O1);inaddition, evokedpotentialofA.kindnervefiberwasstableandlatency wasimmovable.Therewasnosignificantdifferencebefore andafterhigh..frequentandhighintensiveelectricstimulation

    >0.05,Figure6).

    nisalwaysthoughtthatlong.termpotentiationisan importantmodeforlearningandmemoryabilityofcentral nervoussystem.Recentresearchesindicatethatlongterm

    potentiationorlongtermdepressionexistsinpainpathway, cornudorsalemedullaespinalis,hippocampus,amygdala, cerebellum,etc.,andisrelatedtohyperpathia,allodyniaand alganesthesia.Atsuperficiallayer(III)ofcornudorsale

    medullaespinalisinadultrats,highfrequentand

    hi2.intensiveelectricstimulationcancausegenerationof longtermpotentiationoffieldpotentialevokedbyC?kind nervefiber,andthismayberelatedtocentralsensitizationand hyperpathia.

    Atvariousdevelopmentalphases,highfrequentand

    high.intensiveelectricstimulationatsciaticnervecancause

    differentchangesofevokedfieldpotentialatsuperficiallayer ofCOI'llUdorsalemedullaespinalis.Resultsinthisstudy demonstratedthatwhensciaticnerveofratsinthenaenonate groupunderwentelectricstimulation,fieldpotentialofspinal cordevokedbvA.1(indnervefiberwasincreased,latencywas shortened,andcornudorsalemedullaespinaliscouldbe sensibilizedbysuccessiveAfiberstimulation.Thissuggested thatstrongandsuccessivestimulationatnewbornphasecould causedevelopmentalanomalyofdependencystructureof centralnervoussystem;howeveqneuronsofCOrnUdorsale medullaespinalisinadultratscouldonlybesensibilizedby 388

    C.fiberstimulation[13,141.

    Manifestationsofinfantratswere

    similartothoseofadultones.

    Somereferencesrecordedthatperipheralsynapseof embryonicDRGneuronsonthe19impregnationcompletely enteredfoodsiteandendpartofhumanhindlimb,and inherentpartofCOrnUdorsalemedullaespinalisshowed typicalUshapedendoffolliculuspilicentralprocess,which enteredfromCfibertograymatterofcornudorsalemedullae spinalis;however,CfiberlivedtogetherwithAfiberin superficiallayerofcornudorsalemedullaespinalis,untilthe 2lday,Cfibercompletelyoccupiedthesuperficiallayerof cornudorsalemedullaespinalisIl5Cornudorsalemedullae spinaliswaspathwayofprimaryinjuredinformation conductionandlowcenterofprocessing.Akindfiberwas

    mainlylocatedat?一I\/layersofcornudorsalemedullae

    spinalisinadultrats.butatIIIlayersinnaenonaterats.

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