NEURONAL CEROID-LIPOFUSCINOSIS IN THE POLISH-OWCZAREK-NIZINNY (PON) DOG - A RETINAL STUDY

Visual dysfunction and neurological symptoms were found in Polish Owcz arek Nizinny (PON) dogs. Two dogs were examined, one at 2 years of age and the other one at 4 years. The oldest dog was totally blind. The 2 -year-old dog developed mental disturbances and the 4-year-old dog bec ame severely ataxic. Ophthalmoscopical findings were retinal hyper-ref lectivity, attenuation of the retinal vessels and the presence of grey ish to brown spots in the fundus. Electrophysiological and ultrastruct ural studies were performed in the 2-year-old dog. Scotopic ERG respon ses were absent, whereas 30 Hz cone flicker responses were recordable, although with an amplitude reduced to about 30% of the normal level. A slow negative potential replaced the c-wave, indicating a dysfunctio n of the RPE. Intracellular inclusions with a granular appearance or c ontaining membranous fingerprint-like or curvilinear profiles, resembl ing ceroid, were found in different retinal cells. The RPE cells in th e central areas were charged with autofluorescent material having simi lar structure, Photoreceptor degeneration was most severe in the centr al areas, corresponding to the RPE changes. It appears than the PON do g may provide a new animal model for neuronal ceroid lipofuscinosis.