Differences in the retinal GABA system among control, spastic mutant and retinal degeneration mutant mice

Immunocytochemical methods were used to compare the GABA system in control mice and two mutant strains: spastic which has reduced glycine receptors and retinal degeneration mutant in which the photoreceptors degenerate and reportedly have increased GABA and GAD levels. We found that the spastic mutant retina had reduced GABA-immunoreactivity (IR) in the proximal retina, reduced staining for GAD-1440 in the OPL, and reduced GABA(A) receptor staining in the OPL, compared to control, The retinal degeneration mutant retinas had enhanced GABA-IR throughout the retina, particularly in Muller cells, bipolar cells and IPL, and enhancement of GABA(A) receptor staining in the OPL, compared to control. The distributions of GABA-IR, GAD-1440-IR and GABA(A) receptor-IR in retinas of spastic mutant mice that also expressed the retinal degeneration phenotype resembled those found in retinas of mice that expressed only the retinal degeneration phenotype rather than those that expressed only the spastic mutation. No differences were observed among the conditions for GAD-65, GAD-67 or GABA-T, Our results with the spastic and retinal degeneration mutant mice demonstrate that attenuation in the glycinergic system and photoreceptor degeneration, respectively, is accompanied by alterations in different aspects of the BABA system, giving impetus for caution in the interpretation of experiments involving genetic manipulation of complex phenotypes, (C) 1997 Elsevier Science Ltd.