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J. Bilotta, A.C. McCoy, J.D. Houchins, L.M. Garner; Suppression of the ERG d-wave Component Alters the Photopic Spectral Sensitivity of the b-wave Response in Adult Zebrafish . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1900.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Previous work in several species has shown that the b-wave component of the electroretinogram (ERG) response is the result of both depolarizing and hyperpolarizing contributions from various classes of retinal neurons. The purpose of this study was to examine the effects of cis-2,3-piperidinedicarboxylic acid (PDA) on the photopic ERG response of adult zebrafish; in other species, PDA has been shown to suppress the responses of hyperpolarizing bipolar cells and horizontal cells. Methods: Light-adapted adult zebrafish (Danio rerio) received an intravitreal injection of either 0.25 mM PDA or saline. ERG responses to 200 ms flashes of various wavelengths (320-640 nm) and irradiances were obtained. Spectral sensitivity functions were calculated from the log irradiance versus log response amplitude functions of the ERG b-wave component. Results: As expected, PDA injections suppressed the ERG d-wave component. In addition, PDA altered the response characteristics of the b-wave component, but the alterations were dependent on the stimulus wavelength. For example, following PDA injections, the b-wave amplitude was much larger to ultraviolet-wavelength stimuli compared to the pre-injection response. Also, PDA altered the photopic spectral sensitivity based on the b-wave component. PDA reduced the sensitivity of the b-wave component to short-wavelength stimuli, suggesting a reduction in the contributions of the short-wavelength sensitive cones (S-cones) to the b-wave. PDA also increased the inhibitory contributions of the S-cones and middle-wavelength sensitive cones (M-cones) to the opponent mechanisms (Long-wavelength sensitive cones or L-cones inhibited by M-cones, and M-cones inhibited by S-cones) typically found in the ERG b-wave spectral sensitivity function of adult zebrafish. Conclusions: PDA not only suppresses the d-wave component of the ERG response but also alters the response of the b-wave component as well as its spectral sensitivity. The finding that the opponent contributions to the b-wave component are still present following PDA administration suggests that these inhibitory mechanisms are not from hyperpolarizing bipolar or horizontal cells but from neurons in the inner retina, such as the amacrine cells. Finally, these results confirm the notion that the adult zebrafish ERG response, like that of other species, is comprised of "push-pull" contributions from different retinal neurons.
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