Development of rotorod performance in normal and congenitally hypothyroid mutant mice.

Balancing behavior on a rotating cylinder was measured in genetically hypothyroid (hyt/hyt) mutant mice and their phenotypically normal littermates (hyt/+) at 10 different ages between Day 12 and Day 55. Normal mice showed competent balancing behavior in this task by 23 days of age, but mutant hypothyroid mice were incapable of balancing throughout the period of testing. Similar results were found with animals initially tested as adults, indicating that the developmental effects are probably not attributable to different rates of learning. These results are discussed in terms of documented central nervous system abnormalities in animals deprived of thyroid hormone early in life.