Interactions between dissociated rat sympathetic neurons and skeletal muscle cells developing in cell culture: I. Cholinergic transmission☆

[摘要] Sympatheticneurons,dissociatedfromsuperiorcervicalgangliaofnewbornrats,andskeletalmusclecellsweregrowntogetherinmassculturescontainingmanyneurons(ca.1000–3000)andmyotubes,andinmicroculturescontainingonlyonetothreeneuronsandoneorafewmyotubes.Whentheseneuronsgrowundertheinfluenceofcertainnonneuronalcellsmanyofthemacquirecholinergicfunctions;intheabsenceofthisinfluencetheyremainadrenergic.Inthepresentstudy,theinfluenceoftheskeletalmusclecellswassoeffectivethatundercertainconditionsmorethan75%oftheneuronsexpressedcholinergicfunctionasjudgedbytheirabilitytoformexcitatorycholinergicsynapseswithmyotubes(fromratandchick)andwitheachother.Stimulationofsingleneuronsoftengaveriseinthemyotubestosimple(direct)postsynapticpotentials(ejp's)and/orcomplexresponsescomprisingaburstofejp'sthatevokedoneormorespikes;itappearedthatthesecomplexresponsesinvolvedtheactivationofinterneuronalpathways.Inmicrocultures,asingleneuronoftenmadecholinergicsynapseswithitself(“autapse”)and/orwithanotherneuronaswellaswithoneormoremyotubes.Thenicotinicblockingagents,tubocurare(dTC),α-bungarotoxin(α-BuTx),andhexamethonium(C6),attenuatedorabolishedtheejp'satmoderateconcentrations;themuscarinicblocker,atropine,waseffectiveonlyathighconcentrations.Atseveralneuron-myotubejunctions,theacetylcholine(ACh)receptorshaddTCsensitivitysimilartoadultextrajunctionalreceptors;however,whendifferentjunctionswerepooledtheaveragedTCsensitivitywasintermediatebetweenthatofadultendplateandextrajunctionalreceptors.ThejunctionalC6sensitivitywasmuchhigherthanexpectedfromtheactionofthedrugattheadultmammalianendplate.Asinotherstudies,chemicaltransmissionfromneurontoneuronwasalsonicotiniccholinergic,butthenicotinicreceptorsonthemyotubeswerepharmacologicallydistinctfromthoseontheneurons.

[学科分类] 生物科学（综合）