Inhibition by intravenously administered sodium bicarbonate of neuronal activity in medial vestibular nucleus neurons |
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Authors: | A Kawabata T Kishimoto H Ujihara M Sasa S Takaori |
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Affiliation: | Department of Pharmacology, Faculty of Medicine, Kyoto University, Japan. |
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Abstract: | The effects of 7% sodium bicarbonate on medial vestibular nucleus (MVN) neurons were examined to elucidate the mechanism underlying its anti-vertigo action, using alpha-chloralose-anesthetized cats. Intravenous injection of the drug at 1, 2 and 4 ml/kg every 10 min dose-dependently inhibited rotation- and glutamate-induced firing of type 1 neurons, although a low dose of the drug enhanced firing in a few neurons. However, microiontophoretic application of bicarbonate ions did not inhibit rotation- or glutamate-induced firing. After injection of the drug, the Po2 level in arterial blood did not differ from previous levels, but the bicarbonate ion levels dose-dependently increased concomitantly with an increase in pH, as compared with previous levels. These results suggest that the intravenous injection of 7% sodium bicarbonate directly inhibits the neuronal activity of the MVN, although the lower dose may enhance neuronal activity by acting on the peripheral vestibule. |
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