Effects of light deprivation and light damage on the ultrastructure of the inner plexiform layer of rat retina

Chernenko, Garry Allen. (1978) Effects of light deprivation and light damage on the ultrastructure of the inner plexiform layer of rat retina. Masters thesis, Memorial University of Newfoundland.

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Abstract

Four groups of eight male albino rat pups (14 days old) were raised for 8 weeks under different conditions; 1) unsutured, bright light reared (UB), 2) bilaterally lid-sutured, bright light reared (SB), 3) unsutured, dim light reared (UD), and 4) bilaterally lid-sutured, dark reared (SN). The intensity of the bright light was 1960 lux. The intensity of the dim light was equated with that striking the corneas of the SB group (transmission of the sutured rat eye lid is about 0.5%, and was therefore 9.8 lux. All retinas were fixed in osmium, followed by glutaraldehyde and sectioned and stained for light and electron microscopy. Microtomy, microscopy, and scoring were done blind. -- Light microscopy showed that the retinas of both the UB and SB groups were extensively damaged--almost complete degeneration of the outer retinal layers, indicating that even very low intensity light (9.8 lux), when continuous, causes severe retinal damage. The SN group was thicker in many of the retinal layers compared to the UD group. -- Electron microscopy revealed that with the exception of amacrine-ganglion synapses, there are no significant changes in the incidences of any type of synapse in the IPL of the rat retina after light deprivation or light damage. The incidence of amacrine-ganglion synapses was significantly greater (p < .05) in groups UB and SN, only in the outer third of the IPL. -- In light of the present results, plasticity in the rat retina is questionable. If it does exist, it is a very small effect, and is probably reflected by only the amacrine-ganglion synapses.

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