Development of the sympathetic system in the Mexican axolotl, Ambystoma mexicanum☆☆☆

[摘要] Migrationoftrunkneuralcrestcellsinaxolotlembryoshasbeenfollowedbyautoradiographyusinggraftsof[3H]thymidine-labeledneuralfolds.Crestcellsformmelanocytes,dorsalfinmesenchymalcells,spinalganglioncells,andreachthesympatheticregion.Sympatheticneurons,however,arenotidentifiablemorphologicallyuntilabout6weeksposthatching,in24-mmlarvae.Atthisstage,neurons,althoughfew,havecharacteristicultrastructureandreceivesynapses.Thediffusegangliaalsocontaininnervatedchromaffincells;thesedifferentiateearlier,afewdaysposthatching,in14-mmlarvae.Athirdtypeofcellisofmorphologicallyindifferentappearance.Catecholamine-specificformaldehyde-inducedfluorescencefirstappearsclearlyat14mm;withgrowth,thenumberoffluorescentcellsincreases.Seriesoflarvaewereinjectedintraperitoneallywithnervegrowthfactor(NGF),six30-unitinjectionsover2weeks.NGFtreatmentincreasesthenumberofneuronsapparentin24-mmlarvae.Furthermore,differentiatedneuronsoccurinNGF-treated20-mmlarvae(about4weeksposthatching),whentherearenoneincontrols.Theearlyappearanceofdifferentiatedchromaffincellsandtherelativelylateappearanceofdifferentiatedsympatheticneuronssuggestthatadrenergicfunctionsduringthefirstfewweeksoflarvallifearecontrolledhumorallybythechromaffincells,andthatat24mm,neuronsbegintoprovidefaster,finercontrol.

[学科分类] 生物科学（综合）