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KMID : 0376219820190040639
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Chonnam Medical Journal
1982 Volume.19 No. 4 p.639 ~ p.645
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Responses of the Extraocular Rectus Muscles to Mechanical Stretching in Decerebrate Rabbits
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Abstract
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This experiment was designed to explore whether the extraocular muscles elicit stretch reflex action in response to mechanical stretching, as in other skeletal muscles. In the intact and decerebrate rabbits, extraocular rectus muscles were subjected to mechanical stretching, and tension and electromyographic reactions were recorded simultaneously. To make the comparison, the ocular muscle responses to the stimulation of a given vestibular canal nerve, and the triceps muscle responses to a similar stretching were recorded in two separate procedures. The following results were obtained.
1. In the undecerebrate animals, the mechanical stretching caused marked increase in tension of inferior rectus muscle, while the EMG activity remained unchanged.
2. Both the tension and EMG activities of a superior rectus muscle increased simultaneously in response to the electrical stimulation of a ipsilateral canal nerve.
3. Similarly, in the decerebrate animals, mechanical stretching of the ocular muscles evoked marked increase in tension, which was not accompanied by the concomitant increase in EMG activity.
4. In the undecerebrate and decerebrate animals, the triceps muscle revealed marked increase in tension and the EMG activity in response to a mechanical stretching.
The above experimental results demonstrate that mechanical stretching prodaces marked increase in tension of the extraocular muscles. Such a: tension-increment Was not ascribed to an active reflex contraction but merely to a passive physical reaction of the muscles. Stretch reflex action was not demonstrable in the extraocular muscles of this animal.
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