Changes in cholinergic amacrine cells after rodent anterior ischemic optic neuropathy (rAION).
OBJECTIVE
Displaced cholinergic amacrine cell neurons comprise a significant fraction of the retinal ganglion cell (RGC) layer. Rodent anterior ischemic optic neuropathy (rAION) is an optic nerve infarct, which results in RGC loss in mice. The goal was to determine whether rAION produces changes in amacrine cell neurons.


METHODS
rAION was generated in transgenic mice carrying a cyan fluorescent reporter protein (CFP) gene linked to the Thy-1 promoter, which expresses CFP in RGCs. rAION was induced with standard parameters. Retinas were examined pre-and post-induction by retinal fundus microscopy. rAION induction severity was scored by changes in retinal transparency and RGC loss. Cholinergic amacrine cells were identified via choline acetyltransferase (ChAT) immunohistochemistry. ChAT and CFP expression was evaluated in flat-mounted retinas examined by confocal microscopy and western analysis.


RESULTS
Moderate rAION induction levels (defined as early retention of retinal transparency and <70% RGC loss) did not alter amacrine cell numbers in the RGC layer, but changed the relative levels of ChAT expression by immunohistochemistry. No changes in total ChAT protein were seen. Severe rAION induction (defined as loss of retinal transparency and >70% RGC loss) resulted in a trend toward amacrine cell loss and decreased ChAT protein levels.


CONCLUSIONS
There is wide disparity in mouse rAION induction levels using standardized parameters. Moderate rAION induction levels without direct retinal compromise produces isolated RGC loss, with displaced amacrine cell changes likely due to changes in RGC-amacrine communication. Severe rAION induction results in both RGC and amacrine cell loss, possibly due to intra-retinal ischemic changes.
Bernstein
Steven L
SL
Departments of Ophthalmology, University of Maryland at Baltimore, School of Medicine, Baltimore, Maryland 21201, USA. slbernst@umaryland.edu
Guo
Yan
Y
D000199:Actins / Q000378:metabolism; D025042:Amacrine Cells / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D015153:Blotting, Western; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D004195:Disease Models, Animal; D049452:Green Fluorescent Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D018917:Optic Neuropathy, Ischemic / Q000378:metabolism* / Q000473:pathology; D011950:Receptors, Cholinergic / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology; D018800:Thy-1 Antigens / Q000378:metabolism; D050819:Transcription Factor Brn-3A / Q000378:metabolism
D000199:Actins; C485182:Cyan Fluorescent Protein; C494189:Pou4f1 protein, mouse; D011950:Receptors, Cholinergic; D018800:Thy-1 Antigens; D050819:Transcription Factor Brn-3A; D049452:Green Fluorescent Proteins; D002795:Choline O-Acetyltransferase