Calcium entry initiates processes that restore a barrier to dye entry in severed earthworm giant axons

After severance, axons can restore structural barriers that are necessary f or recovery of their electrical function. In earthworm myelinated axons, su ch a barrier to dye entry is mediated by many Vesicles and myelin-derived m embranous structures. From time-lapse confocal fluorescence and DIC images, we now report that Ca2+ entry and not axonal injury per se initiates the p rocesses that form a dye barrier, as well as the subsequent structural chan ges in this barrier and associated membranous structures. The time required to restore a dye barrier after transection also depends only on the time o f Ca2+ entry. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.