Retinal degeneration in the nervous mutant mouse. IV. Inner retinal changes

We have recently noted that the inner nuclear layer (INL) and the inner ple xiform layer (IPL) were significantly thinner in mice homozygous for the ne rvous defect (nr/nr) than in control (nr/+ or +/+) littermates. Here, we ha ve carried out a series of anatomical studies to further understand these i nner retinal changes. At postnatal day (P) 13. there was no difference in t he inner retina between nervous and control mice, while a significant diffe rence was observed at P30. Similar changes were not seen in other mouse mod els of photoreceptor degeneration. There was a significant reduction in the density of cells in the INL that were stained by antibodies against the in hibitory neurotransmitters GABA and glycine. These results indicate that th e nervous defect causes a degeneration of one or more sub-types of amacrine cells, in addition to the loss of cerebellar Purkinje cells and retinal ph otoreceptors that is known to occur in these mutant animals. Finally, evide nce is provided that photoreceptors die by an apoptotic pathway in nervous mice. (C) 2001 Academic Press.