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Tina I Tsai, Mirella Telles Salgueiro Barboni, Balázs Vince Nagy, Michel J Roux, Alvaro Rendon, Jan J Kremers; Asymmetrical ON/OFF retinal dysfunction in the mdxCv3 mouse model of Duchenne muscular dystrophy. Invest. Ophthalmol. Vis. Sci. 2016;57(12):611.
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© ARVO (1962-2015); The Authors (2016-present)
The dystrophin mouse mutant mdxCv3 exhibits standard scotopic bright-flash electroretinogram (ERG) changes that most closely resemble those recorded from patients with Duchenne muscular dystrophy (DMD). We performed additional ERG paradigms on mdxCv3 mice under various conditions to study further parallels between the mdxCv3 line and human DMD.
Full-field ERGs (Q450 SC, Roland Consult) were recorded in anesthetized (Ket:Xyl, 60:5 mg/kg) mdxCv3 (n=9) and age-matched C57BL/6J wild-type littermates (n=10). Six stimulus protocols were presented: (i) inner retinal-dependent scotopic threshold responses (STR; -5.10 to -4.10 log scot cd.s/m2), (ii) rod scotopic flashes (-3.70 to 0.30 log phot cd.s/m2), (iii) cone photopic flashes (0.30 phot cd.s/m2 flash on a 25 cd/m2 background), (iv) sawtooth flicker eliciting mesopic ON- and Off-responses (1 cd/m2, 4 Hz, 100% contrast), (v) long-flash stimulus for photopic ON-/OFF-responses (200 ms, 100 phot cd.s/m2 on 60 cd/m2), and (vi) sinusoidal flicker stimuli (3–30 Hz, 60 cd/m2, 100% contrast). Transient ERGs were analyzed in terms of their maximum and minimum component amplitudes and implicit times, while steady-state signals underwent Fourier analysis to extract amplitudes and phases of the fundamental component.
The mdxCv3 mice exhibited smaller and slower scotopic ERGs (2-way RM-ANOVA, b-waves: up to -33%, +25±7 ms, oscillatory potentials: ≤-41%, +13±2 ms, all p<0.01) and smaller photopic ERGs (t-test, -28%, p=0.02) of similar timing. The downstream STR was not significantly affected. Interestingly, the timing (+25±4 ms, p<0.01), but not amplitude of the mesopic ON-response was affected, whereas both features were altered in the photopic ON-response (-41% and +14±10 ms, p≤0.04). In contrast, both mesopic and photopic OFF waves were within the norm. Sinusoidal flicker ERGs were altered in amplitude (-45%, p<0.01) but not in phase.
Scotopic, mesopic and photopic ERG changes in the mdxCv3 mice have been further defined. Like in DMD patients, dysfunction is likely restricted to the level of photoreceptor-to-bipolar cell transmission, where neural mechanisms required for mesopic/photopic vision, and ON-/OFF-processing are asymmetrically affected.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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