Zhang Na, Liu Jun-xiu, Ma Fu-rong, Yu Li-sheng, Lin Yu-qing, Liu Kun, Mao Lan-qun
Department of Otorhinolaryngology, Peking University Third Hospital, Beijing 100083, China.
Chin Med J (Engl). 2008 Jun 20;121(12):1120-5.
Ascorbic acid (AA) represents one of the most important enzyme co-factors, antioxidants and neuromodulators and plays an important role in the cerebral system. Increasing evidence has suggested that AA could treat certain kinds of vertigo diseases such as Meniere's disease. To elucidate the neurochemical functions associated with AA in vertigo, the change of extracellular AA in the brain cortex following caloric vestibular stimulation (CVS) was evaluated.
An on-line electrochemical detection was coupled with in vivo microdialysis to continuously monitor the change of extracellular AA in the primary somatosensory (SI) area of guinea pigs following a caloric vestibular stimulation. Sixteen guinea pigs were divided into three groups, i.e., experimental group with irrigation of the ear canal with ice water (0 degrees C) (n = 8), and two control groups, one with irrigation of the ear canal with warm water (38 degrees C) (n = 4) and the other with irrigation of the auricle with ice water (n = 4).
In the experimental group, the ice water irrigation of the left external ear canal induced a horizontal nystagmus towards the right side lasting about 45 seconds. No nystagmus was induced by warm water irrigation of the external ear canal or by ice water irrigation of the auricle. The extracellular AA concentration significantly increased following the ice water vestibular stimulation, reaching a maximum of (130 +/- 20)% (n = 8) of the basal dialysate level (2.61 +/- 0.92) micromol/L (n = 8), lasting at least for an hour. AA level did not change distinctly after the irrigation of the left external ear canal with warm water or the irrigation of the auricle with ice water.
The concentration of extracellular AA in the brain cortex of the SI area increased following the ice water vestibular stimulation. This demonstration may be useful for the investigation of the neurochemical processes associated with AA in the process of vertigo.
抗坏血酸（AA）是最重要的酶辅因子、抗氧化剂和神经调节剂之一，在脑系统中发挥着重要作用。越来越多的证据表明，AA可治疗某些类型的眩晕疾病，如梅尼埃病。为阐明AA在眩晕中相关的神经化学功能，评估了热前庭刺激（CVS）后大脑皮层细胞外AA的变化。
将在线电化学检测与体内微透析相结合，以连续监测热前庭刺激后豚鼠初级体感（SI）区域细胞外AA的变化。16只豚鼠分为三组，即实验组用冰水（0℃）冲洗耳道（n = 8），两个对照组，一组用温水（38℃）冲洗耳道（n = 4），另一组用冰水冲洗耳廓（n = 4）。
在实验组中，向左外耳道灌注冰水诱发了持续约45秒的向右侧水平眼震。外耳道温水灌注或耳廓冰水灌注均未诱发眼震。冰水前庭刺激后细胞外AA浓度显著升高，最高达到基础透析液水平（2.61±0.92）μmol/L（n = 8）的（130±20）%（n = 8），至少持续一小时。向左外耳道灌注温水或向耳廓灌注冰水后，AA水平无明显变化。
冰水前庭刺激后，SI区域大脑皮层细胞外AA浓度升高。这一发现可能有助于研究眩晕过程中与AA相关的神经化学过程。
