2 results
Test of the paired-flash electroretinographic method in mice lacking b-waves
- JENNIFER J. KANG DERWENT, SHANNON M. SASZIK, HIDETAKA MAEDA, DEBORAH M. LITTLE, MACHELLE T. PARDUE, LAURA J. FRISHMAN, DAVID R. PEPPERBERG
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- Journal:
- Visual Neuroscience / Volume 24 / Issue 2 / March 2007
- Published online by Cambridge University Press:
- 19 July 2007, pp. 141-149
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Previous studies of rod photoreceptors in vivo have employed a paired-flash electroretinographic (ERG) technique to determine rod response properties. To test whether absence versus presence of the ERG b-wave affects the photoreceptor response derived by the paired-flash method, we examined paired-flash-derived responses obtained from nob mice, a mutant strain with a defect in signal transduction between photoreceptors and ON bipolar cells that causes a lack of the b-wave. Normal littermates of the nob mice served as controls. The normalized amplitude-intensity relation of the derived response determined in nob mice at the near-peak time of 86 ms was similar to that determined for the controls. The full time course of the derived rod response was obtained for test flash strengths ranging from 0.11 to 17.38 scotopic cd s m−2 (sc cd s m−2). Time-course data obtained from nob and control mice exhibited significant but generally modest differences. With saturating test flash strengths, half-recovery times for the derived response of nobversus control mice differed by ∼60 ms or less about the combined (nob and control) average respective values. Time course data also were obtained before versus after intravitreal injection of l-2-amino-4-phosphonobutyrate (APB) (which blocks transmission from photoreceptors to depolarizing bipolar cells) and of cis 2,3-piperidine dicarboxylic acid (PDA) (which blocks transmission to OFF bipolar cells, and to horizontal, amacrine and ganglion cells). Neither APB nor PDA substantially affected derived responses obtained from nob or control mice. The results provide quantitative information on the effect of b-wave removal on the paired-flash-derived response in mouse. They argue against a substantial skewing effect of the b-wave on the paired-flash-derived response obtained in normal mice and are consistent with the notion that, to good approximation, this derived response represents the isolated flash response of the photoreceptors in both nob and normal mice.
ERG assessment of zebrafish retinal development
- SHANNON SASZIK, JOSEPH BILOTTA, CARLA M. GIVIN
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- Journal:
- Visual Neuroscience / Volume 16 / Issue 5 / September 1999
- Published online by Cambridge University Press:
- 01 September 1999, pp. 881-888
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Research has shown that adult zebrafish have a complex visual system, with two possible opponent mechanisms. Anatomically, zebrafish retina develops in a sequential manner and is immature at hatching. The purpose of the present study was to assess zebrafish retinal development using the electroretinogram (ERG). ERG responses to visual stimuli were obtained from 4–5, 6–8, 13–15, and 21–24 days postfertilization (dpf) zebrafish. Individual waveforms were assessed and compared across the four age groups. Spectral-sensitivity functions were calculated for the a- and b-wave components of the ERG response. Results showed that the ERG waveforms and spectral-sensitivity functions varied with age. While the 21–24 dpf subjects had an ERG waveform that was similar to that of adults, the younger subjects did not. Although there were modest differences in the a-wave spectral sensitivity, substantial differences were found in the b-wave spectral sensitivities across the ages. There was a consistent strong response to ultraviolet wavelengths, while across the remaining parts of the spectrum, there was a gradual increase in sensitivity with age. Also, the 21–24 dpf subjects appear to have adult-like U- and S-cone functions, but were missing the L-M and the M-S opponent mechanisms found in the adult. These results support the findings of the anatomical studies and demonstrate that the zebrafish is a useful model for examining the development of retinal function.