Response properties of horizontal cells in the isolated retina of wild- type and pearl mutant mice
H Suzuki, LH Pinto
1986
Journal of Neuroscience
Intracellular recordings were made from axon bearing horizontal cells in isolated retinas (with retinal pigment epithelium removed) of normal and pearl mutant mice superfused with mammalian ginger's solution. Cells were injected with Lucifer yellow and identified by their morphology and their response waveforms. On impalement, we measured a dark, resting voltage of 25-35 mV. All cells had similar spectral sensitivities that were consistent with the CIE scotopic relative spectral luminosity
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... ion. For stimuli of high irradiance, two types of responses could be distinguished, based on their waveform at stimulus offset. One consisted of a rapid and wavelength-dependent repolarization followed by a small, slow hyperpolarization. The other consisted of a large, long-lived, and wavelength-independent after-hyperpolarization. The former were recorded from the somatic end and the latter from the axon terminal arborization. The spatial distribution of sensitivity was measured in over 100 locations within the receptive field using small stimuli. The area within which sensitivity of the soma was within 0.1 log unit of the maximal sensitivity was larger than that of the soma dendritic field, but the sizes were nearly equal for the terminal arborization. No secondary maximum of sensitivity was noted over the dendritic field of the unimpaled part of the cell. For the terminal arborization, the half-saturating irradiance for diffuse 502 nm stimuli was about 180 photons pm-* set-I, about one-tenth that for the soma. These values are in good agreement with those for cat and rabbit. For pearl mutant mice (in which the photoreceptor synapse is abnormal and the retinal sensitivity, measured using retinal ganglion cell responses, is subnormal in the intact animal but not in the isolated retina), the response characteristics, spectral sensitivity, and absolute sensitivity were indistinguishable from those found in wild-type mice. These latter results show that the normality of the responses of ganglion cells in isolated pearl retinas is not due to, e.g., decreases in signal transmission across the outer plexiform layer that are offset by increases in transmission across a more proximal retinal layer. The results are also consistent with the retinal pigment epithelium being a site of expression of the pearl gene, but they do not preclude another site of expression in the retina. The responses of mouse horizontal cells have not yet been studied, but there are a number of reasons for doing so. The mouse is the best-suited vertebrate animal for genetic studies, with over 500 named mutations available, 13 of which have been shown to affect the visual system in subtle ways that do not involve gross degeneration or generalized "neuromuscular" distur-
doi:10.1523/jneurosci.06-04-01122.1986
pmid:3009732
fatcat:ppwcq5dpyzd53jh7qhzao4fcby