Experimental model of vertigo induced by detached otoconia.

Isolated posterior semicircular canals (psc) of bull frogs were used for a model of positional vertigo. Induced ampullary nerve action potentials were recorded. When the cupula was removed and the saccular otoconia were dropped onto the cilia, excitatory, and inhibitory potentials were evoked by changing the psc positions into canal-down and canal-up, respectively. When the otoconia were allowed to stay on the cupular surface, canal-down and canal-up positions also evoked excitatory and inhibitory responses, respectively. When the otoconia were inserted in the canal and were allowed to move, changing the psc positions likewise evoked responses. However, when one end of the canal was closed, these responses disappeared, indicating the efficacy of canal plugging.