Functional relationship between the retractor bulbi muscle and the vestibular system was investigated in conscious or anesthetized rabbits. Recordings of tension and activity of the retractor muscle by electrical stimulation of the vestibular system or sinusoidal rotation of the whole body were as follows.
Nociceptive ´ stimulation such as pin-prick, electric shock and touch, to a unilateral periorbit elicited retraction of both eyeballs through a simultaneous contraction of bilateral retractor muscles. Normal pattern of the vestibulooculr reflex on the eye, which had only retractor muscles without extraocular muscles, was observed by rotatory stimulation to the vestibular system. Retractor bulbi muscles showed an antagonism between superior and inferior slips, and between medial and lateral slips, by electrical stimulation to the vestibular system or unilateral labyrinthectomy.
These results suggest an existence of functional relationship between the retractor bulbi muscle and the vestibular system, in which the retractor muscle contributes to a rotation of eyeball by assisting extraocular muscles.
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