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1、Long-TermPotentiation12JohnE.LismanandJohannesW.Hell1BrandeisUniversity,BiologyDepartmentandVolenCenterforComplexSystems,Waltham,MA02454,USA,lisman@brandeis.edu2UniversityofIowa,DepartmentofPharmacology,IowaCity,IA52242,USA,johannes-hell@uiowa.edu1IntroductionLong-termpotentiat
2、ion(LTP)isalong-lastingstrengtheningofsynaptictransmis-sionthatistriggeredbybriefperiodsofhigh-frequencysynapticstimulation.Otherpatternsofstimulationcanproducealong-termweakeningofsynapses,aprocesstermedlong-termdepression(LTD)ordepotentiation.Synapsesthushaveastablestrengthth
3、atcanbebi-directionallymodifiedinanactivity-dependentmanner.TherearedifferentformsofLTPatdifferentbrainsynapses.ThisarticlefocusesonLTPfoundatglutamatergicsynapsesintheCA1regionofthehippocampus,themoststudiedformofLTP.Atypicalexperimentstartsbymeasuringthestrengthofagroupofsyna
4、pses.Thisisdonebyfiringasingleactionpotentialinsomeoftheaxonsthatenterthisregion.Theseaxonsmakesynapseswithpyramidalcellsandgenerateanexcitatorypostsynapticpotential(EPSP).ThecollectivestrengthofthesynapsesisdefinedbythemagnitudeoftheaverageEPSP.LTPistheninducedbystimulatingthea
5、xonstofireathighfrequency(typically100Hzfor1s),astimulusreferredtoasatetanus.Remarkably,thisbrieftetanuscausesalong-lastingpotentia-tionofthestrengthofthesynapses.ThesizeoftheEPSPtypicallyincreasesby50%–100%,butcanrisebyasmuchas800%insomesituations.Inthebrain-slicepreparationuse
6、dformoststudies,potentiationpersistsuntilthesliceisnolongerviable(5–12h).LTPcanalsobeinducedinlivinganimals,whereitcanpersistforatleastayear(1).Theevidencethatsuchchangesinsynapticstrengthareactuallyinvolvedinmemoryhasstrengthenedinrecentyears.Studieshaveexaminedtheeffectofalea
7、rningexperienceonsynapsesinthehippocampus.Twogroups(67,225)havedemonstratedthatlearninginducesanLTP-likeprocess,whichreducesthesubse-quentabilitytoexperimentallyinduceLTPatthesesynapses.Thisocclusionsug-geststhatlearning-inducedandexperimentally-inducedpotentiationaffectthesame
8、J.W.Hell,M.D.Ehlers(eds.),StructuralandFunctionalOrgan
