Investigation of central mechanisms underlying compensation in the hemilabyrinthectomized cat

Effect of hypergravity on vestibular compensation in guinea pigs

The effect of hypergravity on vestibular compensation was studied in guinea pigs. Pharmacological labyrinthectomy was performed by injecting chloroform into the middle ear cavity under ether anesthesia. The guinea pigs were exposed to hypergravity on a centrifuge. The animals were divided into four groups: a group stimulated with 2G after labyrinthectomy of the right ear, a group stimulated with 2G after labyrinthectomy of the left ear to evaluate the influence of the centrifugal rotation, a group stimulated with acceleration and deceleration alone, and a control group which was maintained under similar conditions, but without centrifugation. Head deviation and nystagmus were recorded and analysed to assess the process of compensation at 1, 3, 5, 7 and 9 h after labyrinthectomy. The 2G-stimulated group showed faster compensation in head deviation than the control group. In this study, the hypergravity stimulation seemed to facilitate the compensation in head deviation.

Effect of electric stimulation on vestibular compensation in guinea pigs

The effect of electric stimulation on vestibular compensation was studied in guinea pigs. Pharmacological labyrinthectomy was performed by injecting chloroform into the right middle ear under light ether anesthesia. The guinea pigs were divided into four groups: a control group which was not electrically stimulated after labyrinthectomy, a group stimulated with 0.6 mA square wave, a group stimulated with 0.3 mA square wave, and a group stimulated with 0.6 mA pulse wave. Electric stimulation, which started 1 h and 15 min after labyrinthectomy, was given through retroauricular electrodes. Nystagmus and head deviations were recorded and analyzed to assess the process of compensation at 1, 2, 3, 4, 5, 8, 12, 18 and 24 h after labyrinthectomy. Electrically stimulated groups, especially group 0.6 mA square wave and group 0.6 mA pulse wave, showed faster compensation in nystagmus and head-body deviation than the control group. Therefore, in this study, electric stimulation seemed to contribute favorably to vestibular compensation.