Localization of voltage-sensitive calcium channels along developing neurites: Their possible role in regulating neurite elongation☆

[摘要] CalciumactionpotentialswereextracellularlyrecordedfromgrowthconesofdifferentiatedN1E-115neuroblastomacellsmaintainedinmonolayercultures.Extracellularrecordingsalongtheneuritessuggestthatvoltage-activatedCa2+channelsarelessabundantintheprocessesthaninthegrowthcones.InordertoinvestigateifCa2+entryintothegrowthconeplaysaroleintheregulationofneuritegrowth,westudiedthemorphologicalchangesinducedbyexperimentalconditionswhichpermitcalciumentry.Cellsweredepolarizedeitherby30mMpotassium(for10–60min)orbystimulatingthesoma(for20–120min)withanintracellularelectrode.Morphologicalchangesinindividualcellswerefollowedbymeansoftime-lapsevideorecordings.Inmorethan60%oftheexperiments,steady-statepotassiumdepolarizationinducedapronouncedincreaseof20–120%intheareaofthegrowthcone.Thiswasfrequentlyassociatedwithneuriteelongation.However,suchchangescouldnotbedetectedinthepresenceofCd2+concentrationswhichblocktheCa2+channels.Similarresultswereobtainedinthepresenceof2μMoftheCa2+ionophoreA-23187orwhenthecellswererepetitivelystimulated(0.2Hz)inamediumcontaining10−6MTTXand15mMTEA.Localmicroapplication,directlyontosinglegrowthcones,ofadepolarizingsolutioncontaining5mMCa2+alsoledtosimilarobservations.Scanningelectronmicroscopyindicatedthatthedepolarizedgrowthconemembraneswereflattenedandcontainedmarkedlymoreroundedprotuberancesrelativetocontrolcultures.OurresultsindirectlysuggestthatCa2+entrymightbeatriggerintheprocessofneuriteelongation.

[学科分类] 生物科学（综合）