BUS/ldr, a Mutant Mouse Strain Exhibiting Abnormal Behaviors: Behavioral Similarities of BUS Mice and Chemically Labyrinthectomized Mice

The behavioral abnormalities of homozygotes (bus/bus) of mutant bustling mice, BUS/ldr, were characterized in comparison with those of heterozygotes (+/bus) and of chemically labyrinthectomized mice. Homozygotes were 4-fold more active than heterozygotes, as evaluated in an open field (11 × 17 cm) for 24 hr by means of Animex. Homozygotes revealed the lack of righting reflex and of head nystagmus on a rotating board, the frequent backward-moving and the inability to swim, in addition to characteristic behaviors such as circling, head bobbing and head tossing. Bilaterally labyrinthectomized mice behaviorally mimicked BUS homozygotes: The behavioral patterns of operated animals were essentially the same as those of BUS homozygotes with respect to all reflex and locomotor indices employed, suggesting that some peripheral vestibular dysfunction, though unidentified yet, is attributed to abnormal behaviors of BUS mice. Unilaterally labyrinthectomized mice were not hyperactive, nor exhibited circling behavior.