急性低血压对清醒大鼠前庭神经内侧核区谷氨酸和牛磺酸含量的影响

Effect of acute hypotension on levels of glutamate and taurine in the medial vestibular nucleus area of conscious rats

目的:利用脑部微量透析法和高效液相色谱分析法,测定静脉注射硝普钠诱发急性低血压后清醒大鼠前庭神经内侧核区细胞外液标本中谷氨酸和牛磺酸含量的变化。方法:实验于2005-02/09在延边大学基础医学院生理学教研室进行。选用Wistar系雄性大鼠,查随机数表法随机分为正常组、单侧迷路破坏损伤同侧组、单侧迷路破坏损伤对侧组,每组6只。单侧迷路破坏组左侧中耳注入对氨基苯胂酸盐损伤外周前庭器官,2周后进行实验。正常组左侧中耳注入生理盐水。腹腔注射水合氯醛麻醉,行股动静脉插管,用于血压监测和静脉给药,动、静脉插管经皮下向后背穿到头部。经股静脉注射硝普钠使动脉血压下降约30%左右。参照Paxinos&Watson大鼠脑图谱将透析膜的外套管插入到前庭神经核,透析膜的外套管内插入自制的透析导管,利用脑部微量透析法收集样本。参照Jin等方法配制诱导剂,高效液相色谱分析法观察静脉注射硝普钠诱发急性低血压后,前庭神经内侧核区细胞外液标本中谷氨酸和牛磺酸含量的变化。结果:实验纳入18只大鼠中,18只是透析探针准确进入预定区域的动物。正常组动物,静脉注射硝普钠使血压平均下降30%时,前庭神经内侧核区谷氨酸含量明显增加(P<0.01),而牛磺酸含量却明显降低(P<0.05);单侧迷路破坏损伤同侧组,诱发急性低血压后前庭神经内侧核区谷氨酸含量则无明显变化(P>0.05),牛磺酸含量明显下降(P<0.05);单侧迷路破坏损伤对侧组,诱发急性低血压后谷氨酸和牛磺酸含量都明显增加(P<0.05);诱发急性低血压后,损伤侧前庭神经内侧核区谷氨酸无显著性变化,而牛磺酸含量却明显下降,与正常组动物诱发急性低血压时前庭神经内侧核区两种氨基酸含量变化值相比谷氨酸含量变化差异显著(P<0.05),牛磺酸含量变化则不明显(P>0.05)。结论:清醒动物急性低血压影响前庭神经内侧核功能活动的过程中可能有兴奋性氨基酸-谷氨酸神经递质参与。

AIM： To determine the changes of glutamate （Glu） and taurine （Tau） in extracellular fluid sample of medial vestibular nucleus （MVN） in conscious rats with acute hypotensioninduced by intravenous injection of sodium nitroprusside by using the methods of brain microdialysis and high liquid chromatogram analysis. METHODS： The experiment was conducted in the Department of Physiology, Basic Medical College of Yanbian University between February and September. Male Wistar rats were selected and randomly divided into normal control group, ipsilateral （unilateral labyrinthine damage） group and contralateral （unilateral labyrinthine damage） group with 6 rats in each group. Two weeks after that, rats in the unilateral labyrinthine damage group were injured of the peripheral vestibular apparatus by infusing arsanilic acid into the left auris media, and rats in the normal normal group were infused of normal saline into the left auris media and anesthetized by intraperitoneal injection of chloral hydrate. The cannula was inserted from femoral artery and vein, so as to monitor the blood pressure and venous administration. The arteriovenous cannula was inserted subcutaneously via the back and to the head. The arterial blood pressure was decreased by 30% by the injection of sodium nitroprusside via the femoral artery and vein. The trocar sheath of dialyzator was inserted to MVN referring to Paxinos ＆ Watson rat brain atlas, and self-made dialyzed tube was insertedinto the trocar sheath of dialyzator to collect the samples by brain microdialysis method. According to the inductor-preparing method of Jin et al, changes of Glu and Tau in extracellular fluid sample of MVN in rats with acute hypotensioninduced by intravenous injection of sodium nitroprusside was studied by method of brain microdialysis. RESULTS： The microdialysis probe correctly inserted into the given region of 18 enrolled rats. The level of Glu in MVN of rats in the normal group was significantly increased by a 30% decrease of blood pressure induced by intravenous injection of sodium nitroprusside （P 〈 0.01）, while the level of Tau was greatly decreased （P 〈 0.05）. There was no change in Glu level of MVN in rats with acute in the ipsilateral group （P 〉 0.05）, while the level of Tau was remarkably decreased （P 〈 0.05）. In rats with induced acute hypotension of contralateral group, the levels of Glu and Tau were significantly increased （P 〈 0.05）, while no marked change was found in level of Glu in rats of ipsilateral group. However, the level of Tau was obviously decreased, which were significantly different from the changes of Glu and Tau in rats of the normal group （P 〈 0.05）, while changes in Tau was not significant （P 〉 0.05）. CONCLUSION： Glu neurotransmitter, excitatory amino acids, may contribute to the effects of acute hypotension on the activity of MVN in conscious animals.