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Ординатура / Офтальмология / Английские материалы / Retinal Degenerative Diseases Laboratory and Therapeutic Investigations_Anderson_2008.pdf
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M.D. Fischer et al.

68.1 Introduction

Cone dystrophies are an important group of inherited retinal degenerations as they affect visual acuity and color vision due to a functional impairment and subsequent physical loss of cone photoreceptors. In contrast to many other inherited degenerations, rod function and morphology is not affected. The cpfl1 (cone photoreceptor function loss 1) mutant is a naturally arising mouse model featuring a mutation (116-bp insertion) in the cGMP-phosphodiesterase subunit (PDE6C) gene of the cone photoreceptors (Chang et al. 2002). The phenotype was first described as lacking cone-mediated light responses combined with a progressive loss of cone photoreceptors, and thus the cpfl1 mouse was proposed to comprise a model for congenital achromatopsia (Chang et al. 2001). In this study, we provide evidence that the cpfl1 mouse is a valid model for cone dystrophies, based on in vivo functional and morphological data.

68.2 Materials and Methods

68.2.1 Animals

Animals were housed under fluorescent lights in a 12-h light - dark cycle, had free access to food and water, and were used irrespective of gender. All procedures were performed in accordance with the local ethics committee, German laws governing the use of experimental animals, and the ARVO statement for the use of animals in ophthalmic and visual research.

68.2.2 Functional Testing

Electroretinography (ERG) was performed according to previously described procedures (Seeliger et al. 2001). The ERG equipment consisted of a Ganzfeld bowl, a direct current amplifier, and a PC-based control and recording unit (Multiliner Vision; VIASYS Healthcare GmbH, Hoechberg, Germany). Mice were darkadapted overnight and anaesthetised with ketamine (66.7 mg/kg) and xylazine (11.7 mg/kg). The pupils were dilated and single flash ERG recordings were obtained under dark-adapted (scotopic) and light-adapted (photopic) conditions. Light adaptation was accomplished with a background illumination of 30 cd/m2 starting 10 min before recording. Single white-flash stimulation ranged from –4 to 1.5 log cd s/m2, divided into 10 steps of 0.5 and 1 log cd s/m2. Ten responses were averaged with an inter-stimulus interval (ISI) of either 5 s or 17 s (for 0, 0.5, 1, and 1.5 log cd s/m2). For additional photopic bright flash experiments, we used a Mecablitz 60CT4 flash gun (Metz, Germany) added to the Ganzfeld bowl. The intensity used in this photopic bright flash protocol was 4.1 log cd s/m2.