Abstract
Purpose: :
To investigate structural and functional changes of inner retina after SC ablation in mice.
Methods: :
The SC was surgically ablated in 8 C57BL/6J mice 3 months-old under Ketamine/Xylazine anesthesia. Spectral-domain OCT (Bioptigen Inc., Durham, NC) measurements of inner and outer retinal thicknesses were performed before surgery and 5 days, 10 days, and 20 days after . A hollow cylinder of tissue (outer radius 0.65 mm, inner radius 0.2 mm) centered on the optic disk was analyzed. Mean thicknesses were calculated on 100 b-scans spanning the retinal tissue using custom semi-automatic software. The Pattern electroretinogram (PERG) and the photopic flash ERG (FERG) were also recorded.
Results: :
Mean inner retina thickness progressively decreased from 92 ±2.5µm at baseline to a plateau of 87.5 ±1.4µm between 10 and 20 postsurgical days (P<0.05). Outer retina thickness did not change between baseline (127±3.5µm) and 10-20 postsurgical days (123±3.0µm, P=0.22). Twenty days after surgery, the PERG amplitude was reduced by 60 % compared to baseline (P <0.05), whereas the FERG displayed insignificant changes (- 18%, P=0.47).
Conclusions: :
As it is known that SC ablation in adult rodents does not cause RGC death even after many months [Perry & Cowey, 1979], results suggest that chronic deprivation of retrogradely transported neurotrophic factors results in shrinkage of inner retina associated with altered RGC function (PERG). Outer retina thickness and function (FERG) do not appear to be affected by the procedure. This mouse model of neuronal atrophy, together with non-invasive tools to monitor structural-functional changes, is relevant for glaucoma research and other chronic diseases of the optic nerve.
Keywords: superior colliculus/optic tectum • retina: proximal (bipolar, amacrine, and ganglion cells) • electroretinography: non-clinical