Investigative ophthalmology & visual science · 2000
Abnormalities of the photoreceptor-bipolar cell synapse in a substrain of C57BL/10 mice.
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Ruether K, Grosse J, Matthiessen E, Hoffmann K, Hartmann C
Аннотация
PURPOSE: A preferential loss of ERG b-wave was detected in a substrain of C57BL/10 mice. Electroretinographic and histologic techniques were used to investigate this hitherto unknown retinopathy.
METHODS: ERGs were obtained from normal and affected C57BL/10. C57BL/6 mice served also as controls. a-Wave and c-wave analyses were performed. Microscopic investigations were done at two different ages.
RESULTS: In the scotopic ERG, a severe reduction of the b-wave amplitude could be observed, whereas the a-wave was only moderately attenuated ("negative ERG"). With age, the a-wave amplitude further decreased, but the rate of reduction was comparable to normals. Oscillatory potentials were severely altered, and the photopic ERG was absent. The ERG c-wave was comparable to normal. ERG a-wave analysis also revealed a reduced maximum amplitude, but no significant difference of receptor sensitivity. Light microscopy revealed a thinning of all retinal layers but mostly of the outer plexiform layer. The number of photoreceptor nuclei was reduced by one third. Electron microscopy revealed a profound loss of ribbon-shaped synapses between rod and rod-bipolar cells and severely abnormal ribbons in the case of cones.
CONCLUSIONS: The so-called negative ERG was associated with alterations in the synaptic layer between rods and rod bipolars. The absent cone ERG may be due to the altered cone-on-bipolar synapses. The overall thinning of the retina as well as the moderately reduced scotopic a-wave amplitude remain unexplained.
METHODS: ERGs were obtained from normal and affected C57BL/10. C57BL/6 mice served also as controls. a-Wave and c-wave analyses were performed. Microscopic investigations were done at two different ages.
RESULTS: In the scotopic ERG, a severe reduction of the b-wave amplitude could be observed, whereas the a-wave was only moderately attenuated ("negative ERG"). With age, the a-wave amplitude further decreased, but the rate of reduction was comparable to normals. Oscillatory potentials were severely altered, and the photopic ERG was absent. The ERG c-wave was comparable to normal. ERG a-wave analysis also revealed a reduced maximum amplitude, but no significant difference of receptor sensitivity. Light microscopy revealed a thinning of all retinal layers but mostly of the outer plexiform layer. The number of photoreceptor nuclei was reduced by one third. Electron microscopy revealed a profound loss of ribbon-shaped synapses between rod and rod-bipolar cells and severely abnormal ribbons in the case of cones.
CONCLUSIONS: The so-called negative ERG was associated with alterations in the synaptic layer between rods and rod bipolars. The absent cone ERG may be due to the altered cone-on-bipolar synapses. The overall thinning of the retina as well as the moderately reduced scotopic a-wave amplitude remain unexplained.