Congenic strains of RCS rats with inherited retinal dystrophy.

Two congenic strains of RCS rats, RCS-p/+ and RCS-c, have been developed that differ from the parental strain at genetic loci affecting pigmentation. Inbred RCS rats are pink-eyed, while RCS-p/+ rats produce segregating litters of pink-eyed (p/p) and black-eyed (p/+) offspring, and RCS-c rats are albinos. All the strains are homozygous for the mutant form of the retinal dystrophy gene. The black eye pigment in RCS-p/+ rats slows the progression of the retinal degeneration by about 10 days in the posterior retina and by about 30-35 days in the peripheral retina in the superior half of the eye. No slowing of the disease occurs in the inferior half of the eye along the vertical meridian. All the strains are similar in body weight and litter size, and show a low incidence of cataract and microphthalmia.