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M. J. Roux, E. Wersinger, Y. Schwab, A. Rendon, J.-A. Sahel, S. Picaud; Difference in GABA Content Between Horizontal Cells of Four Common Mice Strains. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4586.
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© ARVO (1962-2015); The Authors (2016-present)
In the retina, horizontal cells (HCs) mediate lateral inhibition, a process that reinforces luminance contrast by modulating excitability of the cone photoreceptors. This process was initially thought to be mediated by the inhibitory neurotransmitter GABA, which is found in HCs in the retina of many mammalian and non-mammalian species. However, many reports indicate that GABA is not found in the HCs in the mouse retina. We have decided to re-assess these observations by testing different fixation methods, as well as different mouse strains.
GAD65/67 and GABA were detected by immunohistochemistry in the retina of C57BL/6J, 129 Sv pas, CD1 and Balb/c byJ mice. Fixation was obtained by (i) eyecup immersion after removal of the anterior segments, (ii) intracardiac perfusion of cold fixative, or immersion of retinal slices after 2h recovery in (iii) bicarbonate buffer saline at 25°C or (iv) Ames’s medium at 37°C. In parallel, in situ hybridization for GAD65 and GAD67 were performed in the four mice strains.
GAD65/67 was detected as a low level in 70-80% of HCs in all mice strains. The Golgi apparatus labeling and in situ hybridization results that GAD65 is the main isoform expressed in mouse HCs. GABA was detected in horizontal cells in the four mice strains only after intracardiac perfusion, at a very low level except in the Balb/c mouse retina.
The Balb/c mouse retina is a promising model to study the role of GABA transmission in the outer retina. However, the GABA content of HCs appears to be highly volatile and classical electrophysiological slicing conditions do not allow its preservation.
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