肉毒神经毒素A诱导兔咬肌萎缩及其组织形态学研究

Botulinum toxin A -induced masseter muscle atrophy and its histomorphological changes in rabbits

目的探讨肉毒神经毒素A诱导兔咬肌萎缩及对骨骼肌组织形态学影响。方法健康成年新西兰白兔30只,随机取5只共10个咬肌不作任何处理作为正常对照组(N组),另25只进行肉毒素诱导咬肌萎缩试验,一侧咬肌内注射肉毒毒素A(B组),另一侧注射生理盐水作自身对照(S组)。试验组25只动物分5组,分别进行2周、4周、8周、12周和24周试验,于试验结束时用B型超声测两侧咬肌厚度,切除两侧咬肌称其湿重,并留取部份肌组织做切片进行HE染色、三磷酸腺苷(ATP酶)染色和还原型辅酶I还原酶(NADH—TR)染色,光镜下观察及图像分析。结果 N组与S组咬肌各项指标均无差异,咬肌厚度和湿重测量显示B组咬肌厚度和湿重减少,与N组和S组之间差异有显著性,咬肌萎缩程度逐渐加重,至第12周达到最重,第24周时维持与第12周时相等的水平。切片光镜检查显示肌纤维面积减小。ATP酶和NADH-TR染色见Ⅱ型肌纤维横截面积(CSA)减小,Ⅱb型纤维更加明显,I型纤维无明显变化。结论肉毒素A有肯定的诱导肌萎缩作用．其肌萎缩主要为Ⅱ型肌纤维,对I型肌纤维无明显影响。

Objective To investigate the masseter muscle atrophy and its histomorphological changes induced by botulinum toxin A in rabbits. Methods Thirty New Zealand white rabbits were randomized equally into 6 groups： normal control group （group N）, and 5 test groups （2, 4, 8, 12 and 24 weeks, respectively）; each rabbit of the 5 test groups was injected with botulinum toxin A in one side masseter （subgroup B） and saline in the other side （subgroup S） as self-control. The masseters were detected with B-mode ultrasound imaging for measuring masseter＇s thickness at the end of each group experiment. Then both-side masseters were excised for weighing and sampling. Sample slices stained by HE, ATPase and NADH-TR were investigated under optic microscope and analyzed with image analysis system. Data of subgroup B were compared with subgroup S as well as group N. Results All items of subgroup S were similar to those of group N. Compared with group N and subgroup S, the thickness and wet weight of masseters of subgroup B were found significantly decreased. Detected and analyzed under optical microscope, fiber diameters and cross sectional area （CSA） of type Ⅱb fibers were found reduced. The CSA of type Ⅰ fibers did not change. The degree of muscle atrophy aggravated fi＇om week 2 to 12, but remained no further change in another following 12 weeks. Conclusion Botulinum toxin A injection can induce rabbit masseter muscle atrophy. Type Ⅱ muscle fibers, especially type lIb fibers, appeared a marked atrophy. Type I fibers were hardly affected by botulinum toxin A.