Spontaneous Cerebellar Dysplasias in BrlHan: WIST@Jcl Rats.

Abstract

Focal disturbed laminar architecture in cerebellar vermis was observed in 25 out of 100 (25%) males, and 25 out of 100 (25%) females of BrlHan: WIST@Jcl rats. The cortical molecular and granular layers were haphazardly distributed around the primary and/ or secondary fissures. The stellate and basket cells positively stained with parvalbumin immunohistochemistry were observed exclusively in the separated molecular layer. Purkinje cells were found at the boundary between the molecular and the granular layers. Glial fibrillary acid protein (GFAP) immunohistochemistry revealed disarranged fibers of the Bergman glial cells. Based on the incidence of this spontaneous cerebellar lesion, it was presumed to be related to certain genetic factors of this rat strain. Key words: BrlHan: WIST@Jcl rat, cerebellar dysplasia, Hannover rat BrlHan: WIST@Jcl rat (Han Rat), so-called Wistar Hannover rat, is commonly used in toxicological examination. This strain has several advantages, such as a higher survival rate and a smaller body weight, over those of other rat strains.Dysplastic cerebellum has been reported in diseased conditions such as Fukuyama type congenital muscular dystrophy [6] and normal humans [4,5,10,11]. Similar lesions have also been reported in mutant [7] and normal rats [2,9]. In order to obtain background data for the Han Rat, we conducted histopathological examinations in untreated animals and found spontaneous cerebellar dysplasias. This report describes the histopathologic findings of the cerebellar dysplasias in Han Rats.All animals were purchased from CLEA, Japan, Inc. (Received 8 October 2002 / Accepted 24 December 2002)Address corresponding: Y. Kuwamura, Tanabe Seiyaku Co., Ltd., Safety Research Laboratory, Japan at 4 weeks of age. They were housed in stainless steel cages in a room maintained at 23 ± 2°C, with 50 ± 20% humidity and a 12-h light and dark cycle. They had free access to a standard laboratory diet (CRF-1, Oriental Yeast Co., Ltd., Tokyo) and tap water. All animals were sacrificed under ether anesthesia. Twenty healthy animals of both sexes were sacrificed at 8, 10, 14, 19 and 23 weeks of age. Visceral organs and the central nervous system were removed, fixed in 10% neutral buffered formalin, and embedded in paraffin. The sliced sagittal sections of the cerebellar vermis were routinely stained with hematoxylin and eosin (HE) for light microscopic examination. Immunohistochemistry was performed on the paraffin-embedded sagittal sections of the cerebellar vermis with mouse monoclonal antibodies against calbindin (BioMakor, Israel), and