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Y. Sauve, I. Pinilla, N. Cuenca, R.D. Lund; Pigmentation Allows The Development Of Normal Cone Function In P23H Rats . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5786.
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© ARVO (1962-2015); The Authors (2016-present)
Albino rats heterozygous for a P23H mutation in the rhodopsin gene are extensively studied as models of autosomal dominant retinitis pigmentosa (RP). There is indication that albinism itself might exacerbate the disease. We examined the potential preventive effect of pigmentation on functional deterioration using the electroretinogram (ERG).
Pigmented heterozygous P23H rats were generated by breeding normal pigmented Long Evans (LE) rats with homozygous albino P23H rats (line 1 from Matt LaVail). Using detailed ERG tests, we studied various aspects of rod and cone responsiveness in LE (normal controls) and pigmented heterozygous P23H transgenic rats aged from P18 to P180.
While both rod– and cone–driven ERG responses increased in maximal b–wave amplitudes from P18 to P29, only cone–driven b–wave responses reached developmental maturity in P23H rats (by P29 compared with P21 in LE rats). Flicker fusions were also comparable at P29 (42 Hz). Although double flash–isolated rod–driven responses were already affected at P29 (a– and b–waves peaking to 203 and 564µV, compared with 610 and 998µV in LE rats), they could still be elicited at P180 (a– and b–wave maximal amplitudes of 60 and 211µV; i.e. 10% and 20% of normal values). Photopic responses revealed a slow deterioration after P29. By P180, maximal photopic b–wave amplitudes were still 50% of normal values and flicker fusion at 31Hz compared with 42Hz in normal controls.
Breeding of P23H rats on a pigmented background cone function allows cone function to reach developmental maturity levels as revealed by photopic a– and b–wave, and flicker amplitude and fusion. Taking into account that cone function is normal by P29 and deteriorates slowly over the next 6 months makes the pigmented P23H rat an ideal model to study therapies directed at preserving cone function.
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