2016 Volume 15 Issue 2 Pages 62-70
In humans, body sway is observed in ataxic gait disorder. As gait ataxia develops due to degeneration and loss of cerebellar Purkinje cells in B6-wob/t mice (Wob/t), we measured body sway in these mice. The trajectory length (TL) per unit time in the horizontal direction and the weight variance (WV) in the vertical direction were compared with wild-type C57BL/6J (B6) mice as evaluation parameters. First, a rotarod test was performed to observe the coordinated movement of the four limbs with gait ataxia. The duration of walking on the rotating rod was significantly shorter in Wob/t than in B6 (p<0.001), demonstrating ataxia. In addition, TL and WV in the resting state were measured in an open field. The amplitudes of both body sway parameters were significantly greater in Wob/t than in B6 (p<0.001). Wob/t mice were divided into two groups consisting of training (Ex) and no training (NEx). The Wob/t (Ex) group was subjected to forced gait training to investigate the effect on trunk tremors compared to the Wob/t(NEx) group. The amplitudes of TL and WV were significantly reduced in the Ex compared to the NEx (p<0.05). TL remained significantly different between the Ex and B6 groups (p<0.05), but the difference in WV became insignificant. In contrast, in the standstill state, no difference was noted in either TL or WV among the three groups. Based on these findings, the amplitudes of TL and WV of body sway were greater in Wob/t than in B6. However, the body sway tremors were reduced in Ex after forced gait training compared with NEx. These findings clarified that the cause of gait ataxia in Wob/t was the impact of trunk tremors induced by cerebellar Purkinje cell loss, and that forced gait training reduced the tremors. Regarding the reason for the absence of a significant difference in the TL and WV of body sway in the resting state among the B6, Wob/t(NEx), and Wob/t(Ex) groups, the mice may have been somnolent in the resting state and the cerebellar tremors of Wob/t may have been postural tremors that appear during exercise, similarly to those in humans.