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Objective To study the response of NG2 positive and other glial cells in the facial nucleus after facial nerve axotomy,and explore the changes of the microenvironment in the facial nucleus.Methods Rat facial nerve axotomy models were established.Immunofluorescence double staining,and immunohistochemical staining combined with cresyl violet staining were used to observe the response of NG2 cells and other glial cells,and Western blotting was performed to test NG2 protein expression in facial nucleus at postoperative 1,2,7,14,and 28 days.Results Microglia formed dense circles closely around the injured neurons.Astrocytes formed wreath-like structure near the injured neurons.NG2 protein in the injured nucleus has a regular timephase change and NG2 positive cells showed an extensive detachment of synaptic terminals on the damaged neurons after facial nerve axotomy.NG2 cell response was almost the same as microglia.Conclusions All kinds of glial cells may be involved in the formation of glial scar.NG2 positive cells could insulate the damaged neurons against the potential damage from the excitatory input.
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To observe the glial reactions surrounding facial motor neurons following facial nerve anastomosis. At 1,7,21 and 60 d following facial nerve anastomosis, the recovery process of facial movement was observed, the glial fibrillary acidic protein (GFAP) immunoreactivitywas analyzed by a combined method of fluorescent retrograde tracing and immunofluorescent histochemical stai ning, and the ultrastructure of astrocytes were observed under a transmission electron microscope (TEM), respectively. Postoperatively the function of facial muscles could not return to normal, often accompanied with hyperkinetic syndromes such as synkinesis at the late stage. Motor neurons in every facial subnucleus could be retrogradely labeled by fluoro gold (FG), and displayed an evident somatotopic organization. Normally there was a considerable number of GFAP-positive cells in nonnucleus regions but few inside the facial nucleus region. Postoperatively the GFAP immunoreactivity in the anastomotic side increased significantly, but gradually decreased at the late stage. The ultrastructure of astrocytes in our experiment showed that the sheet-like process of astrocytes invested and protected the injured facial motor neurons. The present study shows that reactive astrocytes undergo some characteristic changes during the process of facial nerve injury and regeneration. The plastic change at the late stage may be involved in the mechanism of synkinesis.
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The facial nerve is mainly composed of motor fibers and is distributed to the muscles of facial expressions. In ophthalmology clinics, orbicularis oculi muscle innervated by the facial nerve is involved in spontaneous and voluntary blinking, winking, and more forceful eyelid closure. To understand pathophysiogy of facial nerve palsy due to brain stem lesion involving nucleus, 50% Horseradish Peroxidase (HRP) was injected into nerve stump innervating orbicularis oculi muscle of cat and serial sections of midbrain were studied with light and dark field of light microscope to examine morphology and distribution of the facial nuclei. The HRP-labelled motor neurons were located exclusively within the intermediate division of the ipsilateral facial nuclei and no labelled neurons were found in the contralateral facial nuclei, in the nuclei of the trigeminal nerve, or any other brain stem nuclei. The mean diameter of HRP-labelled motor neurons was 45 micrometer. Most of them were multipolar in shape containing many dendrites. These result suggest that the intermediate division of ipsilateral facial nuclei play an important role in innervating orbicularis oculi muscle.