面神经在不同功能状态下所需神经元的定量分析

Quantitative analysis of needed neurons under different functional status of facial nerve

目的:利用逆行神经追踪技术检测面神经在不同功能状态下所需的神经元数。方法:实验于2003-04/08在河北医科大学解剖教研室完成。将49只昆明小鼠随机分为正常对照组15只和实验损伤组34只。实验损伤组又分为无瘫痪组9只、不完全瘫痪组10只、完全瘫痪组15只。实验损伤各组小鼠腹腔注射麻醉,于左侧的耳后区暴露面神经主干,用Sugita血管瘤夹对面神经主干分别钳夹30,60和120s。24h后,以鼠的胡须运动和瞬目反射为依据测评其面神经功能。48h后再次测评面神经功能,然后对钳夹损伤侧的面神经分支施以逆行神经追踪剂荧光金。正常对照组不对面神经主干实施钳夹,对其仅施以追踪剂荧光金标记。施以追踪剂荧光金浸润48h后,所有动物麻醉经心脏灌注后取脑组织中含面神经核的脑干部制作连续额状切片,计算整个面神经核的追踪剂荧光金标记神经元总数。结果:49只小鼠全部进入结果分析。①采用Sugita动脉瘤夹对神经的压迫比较温和,而且可以通过改变钳夹时间而产生不同等级的损伤。②直接将追踪剂应用于面神经的方法,可在近侧断端面神经核内标记出恒定数量的神经元。③面神经内追踪剂荧光金标记神经元数量:正常对照组多于无瘫痪组、不完全瘫痪组、完全瘫痪组犤(521.7±6.4),(374.1±17.5),(198.6±8.9),(41.1±13.0)个/只,U=24.478,98.989,128.468,P<0.0001犦,实验损伤组的追踪剂荧光金标记神经元数,从无瘫痪组到完全瘫痪组依次递减(U=49.480,U=35.959,P<0.0001;U=27.096,P=0.0002)。将正常对照组小鼠面神经核内的追踪剂荧光金阳性神经元数定为100%,则无瘫痪组、不完全瘫痪组、完全瘫痪组追踪剂荧光金标记神经元所占的百分率分别为56%～85%,31%～47%,0～32%。结论:①应用Sugita动脉瘤夹夹断面神经主干,直接将神经断端浸于追踪剂荧光金溶液中是一种可靠的面神经运动神经元量化神经解剖方法。②当面神经受到损伤时,面神经核内如果有50%左右的正常神经元存在就能维持面神经的正常功能,而当正常神经元数量低于30%时,将导致面神经功能的完全丧失。

AIM： To detect the number of neurons in different functional status of facial nerves with nerve retrograde tracing technique. METHODS： The experiment was performed in the Department of Anatomy of Hebei Medical University from April to August 2004. Forty-nine Kunming mice were randomly divided into normal control group （n=15） and experimental injury group （n=34）. The experimental mice were subdivided into three groups：non-paralysis group （n=9）, incomplete paralysis group （n=10） and complete paralysis group （n=15）. Under intraperitoneal anesthesia, the main trunk of left facial nerve of the experimental mice was exposed at the retroparotid region. The main trunk of the facial nerve was crushed for 30, 60 and 120 s respectively with Sugita hemangioma clip. Twenty-four hours after nerve crushing, the facial nerve function of the mice was estimated on the basis of whisker movement and nictating reflex. Forty-eight hours after nerve crushing, the facial nerve function was assessed again, and Fluoro-Gold （FG）, a fluorescent retrograde neuronal tracer, was applied to the facial nerve branch injured by forceps clip. The mice in normal control group were uncrushed, and FG was applied only. Forty-eight hours after FG application, all the animals were deeply anesthetized, and perfused through the heart. The brains stem containing the facial nucleus were removed to make serial frontal slices. The total number of FG-positive neurons in the facial nucleus was counted in the serial sections. RESULTS： All forty-nine mice were involved in the result analysis. ① The pressure of Sugita aneurismal clip was mild on the nerve and could produce various degrees of impairment by changing the duration. ② The method of applying the tracer directly on the facial nerve could produce a constant number of neurons in the facial nucleus of the proximal broken end. ③ The number of FG-positive neurons of the facial nucleus： It was more in the normal control group than that in the non-paralysis group, incomplete paralysis group, complete paralysis groups： （521.7±6.4, 374.1±17.5, 198.6±8.9, 41.1±13.0, U=24.478, 98.989, 128.468, P 〈 0.000 1）. The number of FG-positive neurons of mice in the experimental injured group showed a steady decline in turn from non-paralysis group to complete paralysis groups （U=49.480, U=35.959, P 〈 0.000 1; U =27.096, P =0.000 2）. When the FG-positive neurons of the normal control group were assumed to represent 100%, these neurons in the non-paralysis group, the incomplete paralysis group and the complete paralysis group accounted for 56%-85%, 31%-47%, and 0-32%, respectively. CONCLUSION： ① It is a reliable anatomic method to count the number of the facial motoneurons by using Sugita aneurysm clip to clamp facial nerve trunk and the tracer directly to the broken facial nerve. ② It is found that when the facial nerve is injured,the neural function of normal facial nerve is maintained if normal neurons of facial nucleus account for about 50%, while complete facial paralysis occurs if the quantity of normal neurons are reduced to less than 30%.