Afferent innervation shapes the dendritic branching pattern of the Medial Giant Interneuron in grasshopper embryos raised in culture☆

[摘要] IntheadultgrasshoppertheMedialGiantInterneuron(MGI)receivessynapticinputfromtheperipheralsensoryneuronsofthecercus.Wepreventedthisinnervationingrasshopperembryosbycuttingoffoneorbothcerciatastagewhenthefirstsensoryaxonsarejustbeginningtoreachthecentralnervoussystem(CNS),andtheMGIhasnotyetformeditsmaturebranchingpattern.Followingthisoperationtheembryoswereraisedinvitrofor3–9days,andtheMGIinjectedwiththefluorescentdyeLuciferYellowtodetermineitsmorphology.ThedevelopmentofthedeprivedcellswasthencomparedtothatofthenormalMGI(describedinM.ShanklandandC.S.Goodman,1982,Develop.Biol.,92,483–500)andofcultured,butunoperated,controlstoascertainwhetherthesepresynapticaxonsinfluencetheembryonicgrowthandbranchingoftheMGI'sdendrites.Theresultsoftheseexperimentsshowthatdendriteformationisenhancedinregionsoftheneuropilcontainingsensoryaxonterminalsandthattheafferentsexerttheirinfluencelocallyonrestrictedportionsofthebranchingstructure.Theenhancedgrowthofinnervateddendritesappearstooccurattheexpenseofdendriticoutgrowthelsewhere,suggestingthatthegrowingdendritesmaybecompetingforalimitedsupplyofsomecellularcomponentnecessaryforcontinuedgrowth.Thus,theMGI'sfinalbranchingpatternisatleastpartiallydictatedbythespatialdistributionofpresynapticaxonswithintheembryonicnervoussystem.

[学科分类] 生物科学（综合）