Retinal Abnormalities in Brown Norway Rat

Abstract

Purpose: : Brown Norway (BN) rat is one of the commonly used laboratory rats in ophthalmic research. We report here its retinal abnormalities.

Methods: : BN rats from 3 suppliers as well as Lewis rats were used to compare their retinal morphology, in vivo angiography and retinal function (assessed by electroretinogram, ERG). Retinal Muller glial cell and neurons were characterized using immunofluorescence.

Results: : BN rats from Janvier and Charles River showed retinal lesions beginning at postnatal day 15 with irregular formation of photoreceptor outer segments, followed by disorganization of outer nuclear layer and inner nuclear layer in young rats and retinal dystrophy and cysts in older rats (6 months). Immunohistochemical analysis showed Muller cell gliosis and hypertrophy, loss of cones, rods and their synapses, and disorganization of bipolar and amacrine cells in the inner nuclear layer. These abnormalities could not be prevented by protection of animals from light. In vivo fluorescein angiography showed punctate diffusions and base ERG demonstrated severe reduction of b wave amplitude. BN rats from Harlan Laboratories also showed mild retinal morphological and vascular alterations, but at older age.

Conclusions: : The pigmented BN rats are widely used for pharmacologic and toxicologic studies. However, we found that BN rats from different origins present various severity of progressive retinal lesions that would certainly interfere with such studies. The causes of the retinal abnormalities in BN rats are under investigation.

Keywords: retina • degenerations/dystrophies • development