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KMID : 0811720020060000156
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Korean Journal of Physiology & Pharmacology
2002 Volume.6 No. 0 p.156 ~ p.0
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Changes in Electrical Activity of the Vestibular Afferent Nerve following Acute Hypotension in Rat
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Jin Yuan-Zhe
Kim Jae-Hyo
Yang Wom-Ki
Lee Sung-Ho
Park Byung-Rim
Kim Min-Sun
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Abstract
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The vestibular system is involved not only body in the control of posture and movement through vestibuloocular and vestibulospinal reflexes but also in the regulation of blood pressure and respiration through vestibuloautonomic reflex. In this study, electrical activity of the afferent vestibular nerve was measured after pretreatment with kynurenic acid (KYN), an NMDA receptor antagonist, to investigate the basic mechanism for the excitation of the peripheral vestibular receptors following acute hypotension induced by sodium nitroprusside (SNP) or hemorrhage, in rats. Acute hypotension was produced by either intravenous infusion of sodium nitroprusside (SNP) or experimental hemorrhage, and the activity of vestibular afferent nerve was recorded by using extracellular single unit recording technique. Mean arterial blood pressure decreased proportionately to the does of SNP or the volume of blood loss, and blood flow of the vestibular system and the cochlear organ changed proportionately to the arterial blood pressure. Intravenous injection of phenylephrine increased blood pressure. Both the vestibular nerve and the cochlear nerve discharged spontaneously and the discharge rates were 75.4±25.3 and 42.3±13.6 spikes/sec, respectively. The vestibular nerve showed direction-specific response to sinusoidal rotation, such that discharge rate increased by rotation toward ipsilateral to recording site, and decreased by contralateral rotation. Acute hypotension produced either by SNP or experimental hemorrhage increased the spontaneous activity and the gain in the vestibular nerve obtained during the sinusoidal rotation of whole body. Acute hypotension produced by SNP infusion increased the spontaneous activity of the cochlear nerve, which was identified by its sensitivity to auditory stimuli. However, the acute hypotension induced by SNP or hemorrhage did not change the activity of the vestibular nerve after kynurenic acid injection. These results suggest that acute hypotension produced excitation of the vestibular hair cells via glutamate excitotoxicity in response to ischemia. (Supported by Neurobiology Research from the Ministry of Science & Technology M1-0108-00-0001)
Source: Korean Journal of Physiology & Pharmacology.2002 Oct;6(Suppl II):S107-S107
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KEYWORD
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vestibular nerve, ischemia, kynurenic acid, electrical activity
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