Abstract
Abstract: :
Purpose: Earlier studies have shown that the alterations of the visual function in rd7 mice result from a deletion in the photoreceptor cell-specific nuclear receptor gene, Nr2e3 (Akhmedov et al., 2000). Mutations of this gene have been associated with the enhanced S-cone syndrome (ESCS) in humans (Haider et al., 2000). Immunohistological studies also showed that the rd7 retina has increased number of S-cone cells (Haider et al., 2001). The purpose of this study was to examine the physiological properties of the S- and M-cones in rd7 mice electrophysiologically. Methods: Scotopic and photopic intensity-response curves were obtained from ERGs recorded from 8-10 weeks rd7 and control mice. S- and M-cone ERGs were elicited by photostrobe flashes with 405 and 520 nm narrow-band interference filters (half-bandwidth: 10 nm) on a rod-suppressing white background. Results: Rod responses were recordable in the rd7 mice although the a-waves were reduced to about one-half of the control, and the b-waves to 80% of the control. The amplitudes of the cone responses for rd7 did not differ from those for control mice. The amplitudes of both S- and M-cone ERGs of the rd7 mice did not differ from those of the control mice. Conclusion: These results indicate that rd7 mice do not demonstrate a prominent "enhanced S-cone" function as in human ESCS.
Keywords: 396 electroretinography: non-clinical • 316 animal model • 562 retinal degenerations: hereditary