Abstract
An inner ear disorder is one of the main causes of vertigo. Though it has not been proven, many of the inner ear disorders are probably induced by ischemia or virus infection. It is not easy to evaluate the circulation of the vestibule because of its anatomical location. The objectives of the current study were to establish a vestibular ischemia model using the bullfrog, and to investigate changes in the vestibular apparatus in the ischemic condition. Bullfrogs (Rana catesbeiana) were used. Under anesthesia with ether, the unilateral temporal bone was opened from the oral cavity by drilling to expose the vestibular nerve. The vestibular artery on the nerve was cut (vestibular ischemia model). In some cases, the vestibular artery was not cut (sham surgery). The intact temporal bones served as controls. Two to 7 days later, the semicircular canals were removed. The cupulae were stained with India ink and investigated in frog Ringer solution. The ampullae were fixed, cut into 4μm slices and stained with hematoxylin-eosin. Neuroepithelia of the ampullae were investigated under the light microscope. In the vestibular ischemia model, 30-50% of cupulae in each semicircular canal were damaged to various degrees. In the sham surgery and control groups, no cupula was damaged. The neuroepithelia of the ampulla were damaged in 50-80% of the vestibular ischemia model and 1 sham surgery, and were intact in controls. Cupulae were damaged easily when the damage to the neuroepithelia was extensive. Vestibular ischemia can damage both the neuroepithelia and cupulae.
