Several mutations causing both photoreceptor degeneration and malfunction have been identified in humans and animals. Although intraocular injection of trophic factors has been shown to reduce photoreceptor death in a few conditions of rapid photoreceptor loss, it is unclear whether long-term beneficial changes in functional properties of affected photoreceptors can be obtained by treatment with these factors. The rds/rds mouse is a spontaneous mutant bearing a null mutation in the rds/peripherin gene, which is linked to many forms of dominant retinal degenerations in humans. Here, we report that intraocular adenovirus-mediated gene transfer of ciliary neurotrophic factor (CNTF) in this mutant reduces photoreceptor loss, causes a significant increase in the length of photoreceptor segments, and results in a redistribution and an increase in the retinal content of the photopigment rhodopsin. These effects are accompanied by a significant increase in the amplitude of the a- and b-waves of the scotopic electroretinogram. These results suggest that continuous administration of CNTF could potentially be useful for the treatment of some forms of retinal degeneration.

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Our results indicate that LE and SD rats differ in their rapidity to dark-adapt, a finding that could explain the previous claim that SD rats were night blind. The reduced bio-availability of calcium ions in eyes lacking melanin could explain this difference. Calcium was previously shown to play a key role in retinal adaptation processes.

Our results thus confirm that despite its relative maturity at birth (compared to rodents), the retina of newborn albino guinea pigs undergoes significant postnatal maturation modifying its structure as well as its function, albeit not as extensive as that previously documented for altricial animals.