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E.-O. Ropstad, E. Bjerkås, A. Bruun, K. Narfstrøm; Immunohistochemical and Electroretinographic Studies of the Standard Wire Haired Dachshund With Inherited Early Onset Cone-Rod Dystrophy. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4516.
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© ARVO (1962-2015); The Authors (2016-present)
To describe electroretinographic (ERG) and morphologic findings in a strain of Standard Wire Haired Dachshund (SWHD)-derived dogs, selected for inherited early onset cone-rod dystrophy (crd).
Nineteen affected and 13 age-matched control SWHDs were subjected to standardized bilateral Ganzfeld ERGs at the ages of 5, 8 and 52 weeks under general anesthesia. Specimens from eyes of crd affected dogs and controls sacrificed at 16 and 52 weeks were evaluated immunohistochemistry using the following antigens: Rho-63 (rods), PNA (cones), PKC (bipolar cells) and GFAP (glia cells).
Photopic cone-derived ERG amplitudes were significantly lower in affected dogs and never reached similar levels as those recorded in control dogs. Affected dogs showed no age related increase in amplitudes using flicker stimuli, while the control groups’ photopic b-wave amplitudes recorded at 50.1 Hz flicker increased significantly with age. Affected animals displayed significantly lower scotopic rod-derived amplitudes for most recordings compared to the control dogs. A- and b-wave implicit times were significantly increased in the youngest affected group compared to age-matched controls at 0.6 log cd*s/m2 and 5.1 Hz single flash light stimuli. Control dogs showed a significant shortening in a-wave implicit times from age 5 to 8 weeks, and in a- and b- wave implicit times recorded at 5.1 Hz single flash stimuli from age 5 to 52 weeks. Immunohistochemically, retinas from affected dogs showed reduced immunostaining using PNA and PKC, an increase using GFAP, while there was no difference concerning the Rho-63 antibody between affected and normal dogs.
The described retinal degeneration in the SWHD is an early onset crd, initially affecting the cone system most severely. Early functional changes are seen in the rod system as well as the inner retina with findings indicating early postsynaptic functional changes. The present study further indicates that the canine retina reaches maturity later than previously reported, or that major breed differences exist.
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