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JJ Kang Derwent, SM Saszik, MT Pardue, LJ Frishman, DR Pepperberg; Response Properties of Rod Photoreceptors in Nob Mice Determined by Paired-flash Electroretinography . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1838.
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Purpose: The corneally recorded electroretinogram (ERG) of the recently described nob mouse (ref.1) is characterized by the absence of the b-wave. The present experiments were undertaken to determine the time course and sensitivity of the nob rod response derived using the paired-flash ERG technique. Methods: ERG a-wave responses to full-field stimuli were recorded from dark-adapted nob and control mice. The full time course of the derived rod response was obtained for three test flash strengths (0.11, 2.6 and 17 sc cd s m-2). The amplitude-intensity relation was obtained with a test-probe interval of 80 ms. Time course data also were obtained after intravitreal injection of L-2-amino-4-phosphonobutyrate (APB) (1.5 µl of 22-27 mM solution), a blocker of responses from depolarizing bipolar cells. Results: nob ERG responses to single flashes were similar to those described previously (1). The normalized amplitude-intensity relation determined for nob was similar to that determined for control mice, and was approximately described by a saturating exponential with half-saturation at a test flash strength near 0.11 sc cd s m-2. The time course of the nob derived rod response was slightly longer than that of controls for all three investigated test flash strengths. For example, with a test flash of 2.6 sc cd s m-2, the time required for 50% recovery from saturation was ∼100 ms longer in nob than in controls. Treatment with APB did not substantially alter the time course of the nob derived response. Conclusion: The nob phenotype is not associated with a marked abnormality in either the investigated amplitude-intensity relation or the full time course of the derived rod response. These results, and the data obtained with APB, are consistent with (i) the absence of a post-receptoral ON pathway contribution to the a-wave of the nob ERG, and (ii) the absence, in normal mice, of a substantial skewing effect of the b-wave on the rod response derived using the paired-flash ERG method. (1) Pardue et al. (1998) IOVS 39: 2443-2449.
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