Abstract
Abstract: :
Purpose: To demonstrate the structural and immunocytochemical changes associated with light-induced retinal degeneration in albino rats. Method: Male Wistar rats aged 3 months, 6 months and 10 months maintained on a normal 12 hr light/dark cycle, in normal animal house lighting conditions, were killed by an overdose of sodium pentobarbital (150 mg/KgIP). The eye cups fixed with 4% paraformaldehyde or 2.5% glutaraldehyde. Tissues were examined either by iummunocyochemistry, with antibodies to neuronal and glial markers, or by conventional histological analysis. Results: As expected we show that with increasing age many photoreceptors are lost. This is accompanied with loss of RPE cells and RPE integrity. Müller glial cells (identified by GFAP and GLAST labelling) extended processes through gaps in the RPE, into the choroid. Immunolabelling for GABA, glycine and the glycine transporter Glyt-1 revealed the presence of numerous neuronal somata and processes which appeared to be migrating, or to have migrated into the choroidal region. Apparent myelination of retinal ganglion cell axons was also observed, especially in peripheral retina, suggesting that oligodendrocytes or their precursors were able to enter the retina, possibly via the compromised blood-retina barrier. Conclusions: We demonstrate that in response to light damage which kills RPE and photoreceptor cells, other adult retinal neurones, which we assume to be mainly amacrine cells, are apparently able to migrate out of the retina along the processes of Müller cells. Processes of presumptive ganglion cells also appear to remodel and may stratify in the choroidal region. Concomitant with this, myelination is evident. This supports earlier studies which have demonstrated the initiation of myelination in the retina when penetrating lesions of the choroid/schlera are present. We suggest our findings are of broad significance when determining the likely events in transplantation of neurones, in the retina and elsewhere.
Keywords: 312 amacrine cells • 479 Muller cells • 567 retinal pigment epithelium