Abstract
A frog's posterior semicircular canal was isolated in Frog Ringer's solution and stimulated by mechanical endolymphatic flow through a microsyringe connected to a micromanipulator. The motion of the cupula was visualized by gently injecting India ink into the ampulla.
1. The motion of the cupula appeared to be that of a “swinging door”, with the base of the cupula hinged on the crista.
2. Ampullofugal stimulation induced an action potential from the posterior canal fiber. This potential adapted in 6-7 seconds.
3. During mechanical endolymphatic flow, the cupula maintained its shifted position without swinging back to the neutral point. This indicates that adaptation is strictly sensorineural in origin.
4. An increase in spike discharge was observed when the canal was stimulated by a piece of frozen Ringer's solution. This indicates that counter flow in the Ringer's solution activated the ampullary sensory cells.
5. Responses from the vestibular nerve trunk were compared with those from the posterior canal fiber. The time course of the response was shorter and the maximum spike count was lower in recordings from the vestibular nerve trunk.
