title: Axonal tracing of the normal and regenerating visual pathway of mouse, rat, frog, and fish using manganese-enhanced MRI (MEMRI).
abstract: OBJECTIVE
  To assess optic nerve (ON) regeneration after injury by applying manganese-enhanced MRI (MEMRI) in a study of comparative physiology between nonregenerating rat and mouse species and regenerating frog and fish species.
  
  
  METHODS
  The normal visual projections of rats, mice, frogs, and fish was visualized by intravitreal MnCl(2) injection followed by MRI. Rats and mice with ON crush (ONC) were divided into nonregenerating (ONC only), and regenerating animals with peripheral nerve graft (ONC+PNG; rats) or lens injury (ONC+LI; mice) and monitored by MEMRI at 1 and 20 days post-lesion (dpl). Frog and fish with ON transection (ONT) were monitored by MEMRI up to 6 months postlesion (mpl).
  
  
  RESULTS
  Signal intensity profiles of the Mn(2+)-enhanced ON were consistent with ON regeneration in the ONC+PNG and ONC+LI rat and mice groups, respectively, compared with the nonregenerating ONC groups. Furthermore, signal intensity profiles of the Mn(2+)-enhanced ON obtained between 1 mpl and 6 mpl in the fish and frog groups, respectively, were consistent with spontaneous, complete ON regeneration.
  
  
  CONCLUSIONS
  Taken together, these results demonstrate that MEMRI is a viable method for serial, in vivo monitoring of normal, induced, and spontaneously regenerating optic nerve axons in different species.
authors.affiliation: Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Axel
authors.initials: A
authors.lastname: Sandvig
authors.forename: Ioanna
authors.initials: I
authors.lastname: Sandvig
authors.forename: Martin
authors.initials: M
authors.lastname: Berry
authors.forename: Øystein
authors.initials: Ø
authors.lastname: Olsen
authors.forename: Tina Bugge
authors.initials: TB
authors.lastname: Pedersen
authors.forename: Christian
authors.initials: C
authors.lastname: Brekken
authors.forename: Marte
authors.initials: M
authors.lastname: Thuen
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology* / Q000648:ultrastructure*; D002712:Chlorides; D003287:Contrast Media; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005399:Fishes; D017895:Manganese Compounds; D051379:Mice; D009416:Nerve Regeneration / Q000502:physiology*; D011898:Ranidae; D051381:Rats; D013045:Species Specificity; D014795:Visual Pathways / Q000166:cytology* / Q000502:physiology*
chemical_list: D002712:Chlorides; D003287:Contrast Media; D017895:Manganese Compounds; C025340:manganese chloride