Cerebellar Hypoplasia in the Hyperbilirubinemic Gunn Rat: Morphological Aspects

Gunn rats, a mutant strain of rats, suffer from autosomal recessive hyperbilirubinemia. The homozygotes (j/j) develop jaundice soon after birth and often exhibit kernicterus and cerebellar hypoplasia that are due to bilirubin. Therefore, j/j Gunn rats have been used as an animal model of bilirubin encephalopathy, as well as of neonatal hyperbilirubinemia. In this review, we discuss morphological aspects of the cerebellar hypoplasia that is due to bilirubin and describe the relationship between plasma bilirubin levels and cerebellar hypoplasia, as well as the pathogenesis of cerebellar hypoplasia, including abnormal histogenesis of the cerebellar cortex, abnormalities associated with Purkinje cells and abnormal synaptogenesis in j/j Gunn rats.