The hair cells of the peripheral vestibular apparatus can be destroyed by the intratympanic injection of sodium arsanilate. Under halothane anesthesia, sodium arsanilate (15 mg/50 µl) is injected bilaterally with a 33 gauge needle through the tympanic membrane.
Labryinthectomy is validated behaviorally with two simple tests: 1) the rat is inverted and a Plexiglas sheet apposed to its feet: intact rats right themselves to walk, but a labyrinthectomized rat, even though upside-down, will walk when its feet are in contact with a solid surface; 2) rats are inverted and then dropped 1 m onto a soft foam-rubber cushion: intact rats right themselves in midair and land on their feet, while lesioned rats make no attempt at righting and land on their dorsal side.
Chemical labyrinthectomy is very simple procedure with a near complete destruction of the vestibular apparatus. However, it is very non-specific, destroying both otolithic and semicircular organs, as well as the auditory cochlea [88]. To distinguish the contribution of the various parts of the inner ear, we propose to use mutant mouse strains that have deficits in otolith formation [81] or semicircular canals [13, 89].