Changes in nNOS and NADPH diaphorase in frog retina and tectum after axotomy and FGF-2 application.
We have shown previously that application of fibroblast growth factor-2 (FGF-2) to the cut optic nerve of the frog, Rana pipiens, augments the survival of retinal ganglion cells (RGCs). In this study, we examine the effects of axotomy and FGF-2 treatment upon the distribution of nitric oxide synthase (NOS) and NADPH diaphorase (NADPH-d) activity in the frog retina and tectum. We find that NOS and NADPH-d are largely absent from RGCs but present in amacrine neurons and in retinorecipient tectal layers. Axotomy alone has little effect on NOS expression or diaphorase activity, apart from slightly increasing the levels of expression in a subpopulation of amacrine cells that arborize in the On sublamina of the inner plexiform layer. FGF-2 application to the optic nerve down-regulates NOS expression and activity in the retina and up-regulates it in the tectum, particularly in retinorecipient layers. Electron microscopy of the optic nerve and neurofilament immunostaining of the tectum suggests that FGF-2 treatment increases the number of regenerating retinal axons arriving at the tectum. The effects in the retina and tectum are probably indirect, that in the retina being due to retrograde signaling from RGCs to amacrine neurons, and that in the tectum being due to re-induction of NOS expression in tectal neurons by the arrival of regenerating axons. At this stage, it appears unlikely that these changes in NOS play a role in the FGF-2's survival effect on RGCs.
Soto
Ileana
I
Institute of Neurobiology and Department of Anatomy, University of Puerto Rico Medical Sciences Campus, 201 Boulevard del Valle, San Juan, Puerto Rico.
López-Roca
Teresa
T
Blagburn
Jonathan M
JM
Blanco
Rosa E
RE
D000818:Animals; D001369:Axons / Q000502:physiology; D019771:Axotomy; D015153:Blotting, Western; D002452:Cell Count; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D007150:Immunohistochemistry; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D009416:Nerve Regeneration / Q000187:drug effects; D016900:Neurofilament Proteins / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000201:enzymology; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D011894:Rana pipiens; D012160:Retina / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D012165:Retinal Ganglion Cells / Q000187:drug effects; D013477:Superior Colliculi / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*
D016900:Neurofilament Proteins; D016222:Fibroblast Growth Factor 2; D052248:Nitric Oxide Synthase Type I; D009252:NADPH Dehydrogenase