Cerebellar hypoplasia and motor development in congenitally jaundiced Gunn rats

Abstract Motor development was observed in 2 groups of Gunn rats (jaundiced and controls) for 5 min/day on Days 1–21 in an open field situation. It was also assessed by their capacity to descend a vertical rope from Day 12 on. After the test, the jaundiced rats had about half of the control cerebellar weight and about 10-fold bilirubin concentration in the cerebellum. Lifting and righting were present on Days 1–4 in both groups. Pivoting increased rapidly on Days 5–6 in both groups, and disappeared rapidly from Day 10 in the controls but it disappeared much more slowly in the jaundiced rats. Although readiness for walking was not retarded in the jaundiced group, tumbles during locomotion were seen often between Days 7–15 in the jaundiced rats, and they were rarely seen on Days 6–9 in the controls. In the rope descent test, the jaundiced rats evidenced more primitive modes of descent (fall and backward descent), and descended head-down (normal adult pattern) less than controls over trials.