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KMID : 0376219830200020297
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Chonnam Medical Journal
1983 Volume.20 No. 2 p.297 ~ p.307
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Studies on Relevancy of the Semicircular Canals and Extraocular Muscles to Horizontal PAN in the Rabbits.
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Abstract
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In rabbits injected with alcohol (1.6g/kg, B.W. , i. v. ), typical PAN(Positional Alcohol Nystagmus) was elicited in response to passive rotation of the head to left side down or right side down position in recumbent posture. By means of nystagmographic observations, relevancy of the semicircular canals and extraocular muscles to the nystagmus was explored in various experimental procedures, and the following results were obtained.
1) Rotation of the head to lateral direction (either to left or right) elicited horizontal PAN; depending upon the direction of head rotation, nystagmus was reversed to opposite direction.
2) Returning rotation of the head back to original position also elicited the horizontal PAN. The direction of the nystagmus was the same to that observed in the rotation of head to the lateral position.
3) Strong response of the horizontal rectos muscles and weak response of the vertical rectos muscles were demonstrated during the horizontal PAN caused by the lateral head rotation.
4) Upon resecting the horizontal rectos muscles of the eye, the horizontal PAN was converted to vertically oriented nystagmus.
5) When the unilateral horizontal canal was plugged the horizontal PAN was not abolished. Plugging the bilateral horizontal canals, however, converted the horizontal PAN to nystagmus with vertical orientation.
These experimental results indicate that vestibulo-ocular reflex connection between the horizontal canals and horizontal rectos muscles may play important roles in eliciting horizontal PAN caused by the lateral rotation of the head in recumbent posture in this animal.
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