Abstract
Abstract: :
Purpose: To compare the morphological and functional recovery of the retina after detachment and reattachment in the cone dominant ground squirrel. Methods: Ground squirrel retinas were detached for 1 day and reattached for 7, 35 or 90 days (n=2, each timepoint). ERGs were recorded using cone-isolating flicker at 1 day after the detachment and on a weekly basis after the reattachment. Contrast/response functions were measured for both S and M cones. At the end of the experiment, retinas were prepared for light microscopy or immunocytochemical staining with antibodies to S and M cone opsins, cytochrome oxidase, synaptophysin, GFAP, CRALBP, IRBP and the lectin PNA. Photoreceptor density maps were created from wholemount preparations immunostained with biotinylated PNA and anti-S cone opsin. Cell counts of photoreceptor nuclei and cone outer segments (OS) were compared to the ERG contrast/response functions. Cell death was examined using the TUNEL method. Results: S and M cone OS showed a gradual recovery in length following reattachment and this recovery could be followed using the ERG. There was a significant linear correlation between ONL cell counts and ERG contrast gain values (P<0.01). In addition, M cone OS number from retinal wholemount counts showed a significant linear relationship to the ERG contrast gain values (P<0.05). However, while the ERG recordings peaked within the first 2 weeks of reattachment, OS lengths had not fully recovered at that time. Reattachment also stopped photoreceptor cell death and reversed the disruption of interphotoreceptor matrix as well as the distribution of some Müller cell proteins. It also appeared to activate some astrocytes based on anti-GFAP staining. Conclusion: This study demonstrates that the ERG can be used to specifically follow the recovery of cone photoreceptors following detachment and reattachment. The recovery of the ERG, however, occurs much more quickly than the recovery of OS length suggesting that OS number is more critical in eliciting a normal ERG than OS length.
Keywords: 563 retinal detachment • 517 photoreceptors • 561 retinal degenerations: cell biology