Responses of the lateral rectus muscle elicited by stimulations of bilateral vestibular nerves in cats

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  • 両側前庭刺激に対する外直筋の反応

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In previous work, the muscular activity in the slow phase and fast phase of nystagmus was explicated through the range of the rise time course and the pattern of muscular contraction, the phenomena of which were elicited by electric stimulation to the horizontal ampullary and abducens nerves.<BR>The present study was undertaken to observe the responses of the lateral rectus muscle elicited by stimulations of the bilateral vestibular nerves. The cats were anesthetized with pentobarbital sodium (35mg/kg). The condition of the electric stimulation to the left horizontal ampullary nerve was a pulsetrain of 200msec or more at 100-500Hz with pulses of 0.5msec, and to the right horizontal ampullary nerve was a pulse-train of 75msec duration at a delay of 100msec from start of the left side stimulation. The responses of the right lateral rectus muscle were recorded through the mechanogram and EMG. The activities of the lateral rectus muscle elicited by stimulation of the contralateral vestibular nerve were decreased by stimulation of the ipsilateral vestibular nerve. The rates of decline ranged from 33.3-93.7%, especially, from 78.1-93.7% to the ipsilateral stimulation of high frequency at 300Hz or more, and also the spike discharges disappeared. The half decay times ranged from 15-45msec, and on the short side at the ipsilateral stimulation of high frequency. The range was similar to the half decay times in the fast decay phase of nystagmus. Following cessation of the ipsilateral stimulation, the muscular responses elicited by the contralateral stimulation showed only slight increase, the pattern of responses showed recruitment (linear increase) and resembled the slow rise phase in nystagmus. It is suggested that the formation of this recruitment pattern is influenced by the effect of inhibition.

Journal

  • Equilibrium Research

    Equilibrium Research 38 (2), 177-181, 1979

    Japan Society for Equilibrium Research

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