The Enzymatic Histocytochemistry Study Of Oris Muscle After Facial Nerve Denervation

ObjectiveFacial nerve denervation can cause a series of symptoms. The function and histology of facial muscles is changed after facial nerve denervation. But the present study on facial paralysis is mostly limited to the observation of facial nerve and the changes of facial muscles are paid little attention. The oris muscle is a representative muscle in the facial muscles. It is very important to clinical diagnosis. In order to study the histological changes of facial muscles after facial nerve denervation, the following experiments were done. The succinate dehydor-genase(SDH) , acetylcholinesterase (AchE) and Ca2+-ATPase were examined under light and electrical microscopes. The ultrastructure of mitochondria and motor end plate were observed in order to study the energetic metabolism and the pathological changes of oris muscle after facial nerve denervation.MethodsThe models of facial paralysis were made in guinea pigs. Models of facial paralysis were created by pinching the facial nerve for 15s, 30s and cutting off. They were observed in 7 and 30 days. (1) The oris muscle mitochondria structures and their SDH positive products were observed via light and electron microscopes. (2) The specimen was observed via light microscope after being stained with both succinate dehydrogenase ( SDH) and acetylchonlineasterase ( AchE ) by enzymatic histocytochemistry staining method. Then the gradation of AchE content of muscle fibers of different groups was tested via LUZEX - F computer image analysis system. The structure of motor end plate and the AchE positivereactive product was observed via transmitting electron microscope. (3 ) The specimen was observed via light microscope after being stained with Ca2 ± - AT-Pase by enzymatic histocytochemistry staining method. Then the gradation of content of Ca ± - ATPase muscle fibers of different groups was tested via LUZEX - F computer image analysis system. The structure of triplet and Ca ± - ATPase positive reactive product was observed via transmitting electron microscope.ResultsThe enzymatic activity of SDH of m. oris decreased 1 week after denerva-tion and resumed 1 month later. The degree of damage was; the excision group > the compression group for 30 s > the compression group for 15 s while the degree of rehabilitation was; the compression group for 15 s > the compression group for 30 s . The mean gradation value of AchE was 60. 4545±4. 3561 in 15s 1w group; that of 30s Iw group was 65. 1818±1.2194, significandy different from the 15s Iw group(p <0. 01) ; that of cutting off group was 72. 8926± 7.3511, significandy different from the 30s Iw group(p <0. 01) ;that of 15s 1m group was 62. 8641±7. 8189, while that of 30s 1m group was 64. 4570 ±2. 2539, and there is significant difference between the two groups( p <0. 01). Under electron microscope, the motor end plate atrophied in cutting off group and AchE positive granules decreased; the motor end plate and AchE positive granules restored evidendy in 15s 1 m group; that of 30s 1m group restored slighdy. The enzymatic activity of Ca2 ± -ATPase of m. oris decreased 1 week after den-ervation and resumed 1 month later,. The degree of damage was: the excision group > the compression group for 30 s > the compression group for 15 s while the degree of rehabilitation was : the compression group for 15 s > the compression group for 30 s .ConclusionsThe longer time the facial nerve is injured and the more serious the degreeof denervation was sustained, the changes of the mitochondria including the changes of SDH would be more serious and more difficult to recover; the facial nerve injury should be managed as early as possible. The severer the degree of denervation is, the severer the change of motor end plate and the worse the prognosis is, which suggests the early application of facial nerve decompression. The loss of m. oris enzymatic activity was related with the degree of facial nerve injury. It suggests that with the anatomic and physiological changes of facial nerve, t...