title: Persistence of tracer in the application site--a potential confounding factor in nerve regeneration studies.
abstract: Selective reinnervation of peripheral targets after nerve injury might be assessed by injecting a first tracer in a target before nerve injury to label the original neuronal population, and applying a second tracer after the regeneration period to label the regenerated population. However, altered uptake of tracer, fading, and cell death may interfere with the results. Furthermore, if the first tracer injected remains in the target tissue, available for "re-uptake" by misdirected regenerating axons, which originally innervated another region, then the identification of the original population would be confused. With the aim of studying this problem, the sciatic nerve of adult rats was sectioned and sutured. After 3 days, to allow the distal axon to degenerate avoiding immediate retrograde transport, one of the dyes: Fast Blue (FB), Fluoro-Gold (FG) or Diamidino Yellow (DY), was injected into the tibial branch of the sciatic nerve, or in the skin of one of the denervated digits. Rats survived 2-3 months. The results showed labelled dorsal root ganglion (DRG) cells and motoneurones, indicating that late re-uptake of a first tracer occurs. This phenomenon must be considered when the model of sequential labelling is used for studying the accuracy of peripheral reinnervation.
authors.affiliation: Department of Human Anatomy and Embryology, Faculty of Medicine, University of Barcelona, c/Casanova no. 143, 08036 Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Puigdellívol-Sánchez
authors.forename: Alberto
authors.initials: A
authors.lastname: Prats-Galino
authors.forename: Domingo
authors.initials: D
authors.lastname: Ruano-Gil
authors.forename: Carl
authors.initials: C
authors.lastname: Molander
mesh_terms: D000578:Amidines / Q000493:pharmacokinetics; D000818:Animals; D005260:Female; D005456:Fluorescent Dyes / Q000493:pharmacokinetics*; D009416:Nerve Regeneration / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020426:Sciatic Neuropathy / Q000378:metabolism; D013194:Staining and Labeling / Q000379:methods*; D013266:Stilbamidines; D013979:Tibial Nerve / Q000378:metabolism*
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D000578:Amidines; D005456:Fluorescent Dyes; D013266:Stilbamidines; C031455:diamidino compound 253-50; C037945:diamidino yellow