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KMID : 0376219740110031013
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Chonnam Medical Journal
1974 Volume.11 No. 3 p.1013 ~ p.1023
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Ocular Muscle Response to Posterior Semicircular Canal Excitation in Rabbits
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Abstract
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The present experiment was carried out to explore functional interrelation between the posterior semicircular canal and the extraocular muscles in rabbits. In a group of urethane anesthetized rabbits, a fine insulated wire except the cut. cross section of its tip was introduced into a posterior semicircular canal ampulla as a monopolar electrode, and the ampullary nerve. was subjected to square-wave pulses to simulate the canal excitation. Isometric tension and EMG responses of the extraocular muscles were recorded by means of a physiographic recorder, and the movements of the both eyes were also observed. In an another group of the animal, a minute amount of fluid was injected into or drawn out from a. posterior canal to produce. lymphatic fluid displacement, and the isotonic responses of ocular muscles´ were recorded on a rotating smoked drum. Following results were obtained.
1. Stimulation of a unilateral posterior canal nerve caused contraction of, superior oblique, medial rectus and superior rectus muscles in the ipsilateral eye in the contralateral eye, contraction of inferior oblique, lateral rectus and inferior rectus muscles were demonstrated.
2. Ocular muscle responses :to the ampullofugal flow produced in a posterior canal were similar to those observed by the ´canal nerve stimulation, and ocular muscle responses of opposite pattern were elicited by the ampullopetal flow in the same posterior canal.
3. The ocular muscles of primary contraction were determined depending on the direction of eye movements observed. The superior oblique of the ipsilateral eye and the inferior rectus of the contralateral eye were found to be muscles of primary action during the unilateral posterior canal excitation.
The ocular muscle responses observed by these functional experiments were diagrammatically- retranslated :into Q an excitation. of ocular motor nuclei, and compared to the morphological observations of Carpenter et al. which explored neural connections between the posterior canal and the ocular motor nuclei. When the morphological data of Carpenter et al. were modified to an acceptable form to eliminate some theoretical contradictions found in them, considerable agreement was recognized between the two experimental data of the different approaches.
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