This wok
was supported by the Prominent Youthful Science Foundation of Jinlin Province (No. 20040109).
*Corresponding author. Tel: +86-433-2660586, E-mail: y-z-jin@ybu.edu.cn
Concentration of amino acids changes in the rat medial vestibular nucleus following unilateral labyrinthectomy
1Department of Pharmacology; 2Department of Physiology, Yanbian University College of Medicine, Yanji 133000, Jinlin, 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 pretreated by infusing 2% lidocaine 1.2ml or 10mg arsanilic acid into the tympanic cavity to obstruct uni-periphery vestibular organ, then the levels of amino acids were determined in MVN of normal control and ipsi-/contra-lesional rats. In 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 ml sample, respectively. The concentration of aspartate and glutamate was decreased, and the concentration of taurine was 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 was increased, the concentrations of glycine and alanine were decreased in the contra-lesional MVN, accompanied by imbalances of glutamate, glycine and alanine between the bilateral nuclei. In contrast, decreased levels of glutamate and alanine, but an increase in the level of glutamine in the ipsi-lesional MVN of rats 2 weeks after infusing 10mg arsanilic acid into the tympanic cavity to obstruct uni-periphery vestibular organ, and decreased level of glutamate was seen in the contra-lesional MVN after UL. Furthermore, the level of glutamine in the ipsi-lesional MVN was obviously increased more than that in the contra -lesional MVN. These results demonstrate that an imbalance among different amino acids appeared in bilateral MVN after UL, but this imbalance decreased after the development of vestibular compensation, whereas the imbalance of glutamine release between bilateral nuclei appeared after vestibular compensation.
Key words: amino acids; medial vestibular nucleus; unilateral labyrinthectomy; vestibular
compensation
单侧迷路破坏后大鼠前庭神经内侧核区氨基酸含量的变化
于海玲1，安英2，姜海英2，金清华2，金元哲2,*
延边大学医学院 1药理学教研室; 2生理学教研室，延吉 133000
摘要：本实验用脑部微量透析法和高效液相色谱法观察单侧迷路破坏(unilateral labyrinthectomy, 经利多卡因或对氨基苯砷酸盐预处理以阻断单侧外周前庭器官)后大鼠同侧及对侧前庭神经内侧核（medial vestibular nucleus, MVN）区部分氨基酸天冬氨酸(aspartate)、谷氨酸(glutamate)、谷氨酰胺(glutamine)、甘氨酸(glycine)、牛磺酸(taurine)和丙氨酸(alanine)含量的变化，以了解前庭代偿的部分神经化学机制。实验观察到，对照组大鼠MVN区天冬氨酸、谷氨酸、谷氨酰胺、甘氨酸、牛磺酸和丙氨酸浓度分别为6.15±0.59, 18.13±1.21，33.73±1.67，9.26±0.65, 9.56±0.77，和10.07±0.83 pmol/8ml透析样本。2%利多卡因左侧中耳内灌注后10分钟，同侧MVN区天冬氨酸、谷氨酸含量立即增加（P﹤0.05），牛磺酸含量减少（P﹤0.05）；对侧MVN区谷氨酸含量立即增加（P﹤0.05）, 甘氨酸和丙氨酸含量减少；双侧核团间谷氨酸、甘氨酸和丙氨酸含量失衡。而用对氨基苯砷酸盐永久阻断单侧前庭器官2周后，同侧MVN区谷氨酸和丙氨酸含量减少, 谷氨酰胺含量增高；对侧MVN区谷氨酸含量也减少；同侧MVN区谷氨酰胺含量明显高于对侧MVN区。结果提示，单侧迷路破坏后双侧MVN 区氨基酸含量立即失去平衡,伴随前庭代偿的进展此差异减少,但是在前庭代偿后却出现双侧前庭核区谷氨酰氨的含量失衡,说明在前庭代偿过程中氨基酸含量变化起着重要作用。
关键词：氨基酸；前庭内侧核；单侧迷路破坏；前庭代偿