冷热水前庭刺激对豚鼠前庭内侧核5-羟色胺能系统的影响

Effects of caloric vestibular stimulation on serotoninergic system in media vestibular neuclei of guinea pigs

目的研究前庭神经系统在受到冷热水刺激诱发眩晕后前庭内侧核5-羟色胺的变化规律,探讨神经递质在眩晕发生时的作用。方法利用微透析技术研究冷热水注入豚鼠耳道时对其前庭内侧核5-羟色胺的影响。结果冷热水刺激诱发了豚鼠的前庭性眼震,分别持续60秒和90秒,37℃水灌流外耳道以及冷热水刺激耳廓时均无眼震出现。外耳道灌流44℃热水和0℃冰水在10分钟时显著升高前庭内侧核5-羟色胺水平至基线水平的189％和254％,并且持续升高5分钟。37℃水灌流外耳道以及冷热水刺激耳廓时5-羟色胺水平无明显变化。结论前庭内侧核5-羟色胺水平的升高可能与冷热水刺激末梢前庭系统所诱发的眩晕发生有关。5-羟色胺可能作为一种神经调节物质发挥作用的。

OBJECTIVE To clarify the intrinsic characteristics of 5-HT release in the media vestibular neuclei （MVN） during the period of vertigo induced by caloric stimulation. METHODS In vivo microdialysis technique was used to examine the effects of caloric stimulation on serotoninergic system in MVN. RESULTS In caloric test, the hot water （44℃） irrigation of the right external auditory canal induced horizontal nystagmus toward the right side lasting 60s, and the ice-water irrigation of the right external auditory canal induced it toward the left side lasting for 90s. No nystagmus was induced by hot or ice water irrigation of the auricle or by the external ear canal irrigation with 37℃ water. The MVN 5-HT levels significantly increased to 254% and 189% of baseline by Caloric vestibular stimulation in 10 minutes with ice water and hot water irrigation of external auditory canal ,and it lasted for 5 min.,while no changes were found by irrigation of 37℃ water into the external ear canal or by hot or ice water irrigation of the auricle.CONCLUSION The increases of 5-HT in MVN may be involved in the mechanisms of vertigo induced by caloric stimulation. The consistent increase of 5-HT level suggests 5-HT acts as a neuromodulator.