Spatial responses to light in mice with severe retinal degeneration

It is known that mice homozygous for the retinal degeneration (rd) mutation are able to synchronize their circadian rhythms to light-dark cycles. In the present experiments mice were given a choice of a dark or an illuminated living and nesting area. C3H, CBA and C57 rd/rd mice spent more time in the dark than in the illuminated area. Also, they spent as much time in the dark area as did wildtype controls. This shows that, despite advanced retinal degeneration, light can be used to control behaviour in space as well as in time. This was true of mutant mice over a year old, when retinal degeneration is very severe, and also of a transgenic strain of mice whose rods are destroyed as they begin to develop in the first few weeks after birth.