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Changes of amino acid concentrations in the rat medial vestibular nucleus following unilateral labyrinthectomy

Yu Hailing, An Ying, Jiang Haiying, Jin Qinghua, Jin Yuanzhe

Department of Pharmacology,Yanbian University College of Medicine.Yanji 133000,Jilin;China

Abstract

To understand the neurochemical mechanisms underlying the vestibular compensation, we determined the levels of amino acids such as aspartate, glutamate, glutamine, glycine, taurine, alanine in the medial vestibular nucleus (MVN) following unilateral labyrinthectomy (UL), by using in vivo brain microdialysis and high-performance liquid chromatography technique. Rats were pre- treated by infusing 2% lidocalne 1.2 mL or 10 mg arsanilic acid into the tympanic cavity to obstruct uni-periphery vestibular organ, and then the levels of amino acids were determined in MVN of normal control and ipsilateral or contralateral lesional (ipsi-/contra-lesional) rats. In the control experiment, the levels of aspartate, glutamate, glutamine, glycine, taurine, and alanine were (6.15±0.59), (18.13±1.21), (33.73±1.67), (9.26±0.65), (9.56±0.77) and (10.07±0.83) pmol/8 #mu#L sample, respectively. The concentrations of aspartate and glutamate decreased, while the concentration of taurine increased in the ipsi-lesional MVN of rats 10 min after infusing 2% lidocaine into middle ear to obstruct uni-periphery vestibular organ. Whereas the concentration of glutamate increased, the concentrations of glycine and alanine decreased in the contra-lesional MVN, accompanied by imbalances of glutamate, glycine and alanine in the bilateral nuclei. In contrast, the levels of glutamate and alanine decreased, the level of ghitamine increased in the ipsi-lesional MVN, and the level of glutamate decreased in the contra-lesional MVN of rats 2 weeks after infusing 10 mg arsanilic acid into the tympanic cavity to obstruct m-periphery vestibular organ. Furthermore, the level of glutamine in the ipsi-lesional MVN was obviously higher than that in the contra-lesional MVN. These results demonstrate that an imbalance of different amino acids appeared in bilateral MVN after UL, and this imbalance decreased after the development of vestibular compensation. Whereas the imbalance of glutamine release in bilateral nuclei appeared after vestibular compensation.

Key words: amino acids;medial vestibular nucleus;unilateral labyrinthectomy;vestibular compensation

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Citing This Article:

Yu Hailing, An Ying, Jiang Haiying, Jin Qinghua, Jin Yuanzhe. Changes of amino acid concentrations in the rat medial vestibular nucleus following unilateral labyrinthectomy. Acta Physiol Sin 2007; 59 (1): 71-78 (in Chinese with English abstract).