Expression of ciliary neurotrophic factor in ambiguous nucleus motoneuron after long-term laryngeal denervation / 第二军医大学学报

ABSTRACT

Objective:Ciliary neurotrophic factor (CNTF) plays important roles in the maintenance and survival of motor neurons. This study attempted to explore the expression and distribution of CNTF mRNA and its protein in the ambiguous nucleus(Amb) motoneuron in order to clarify its functional state after long term laryngeal denervation. Methods: The recurrent laryngeal nerves were obtained from dogs. Brain stems were removed and sectioned for histochemistry, immunohistochemistry and in situ hybridization of CNTF. Amb motoneurons were identified by Nissl staining. The count and intensity of positive reactive motoneurons were measured by computer image processing system. Results: Transection of the laryngeal nerve led to a very marked reduction in the count and intensity of CNTF mRNA positive reactive motoneurons, and reached minimal levels at week 3. CNTF immunoreactivity increased rapidly and reached maximal levels also at week 3. At week 4, a significant increase in CNTF mRNA expression and decrease in CNTF immunoreactivity were observed. At week 6, both CNTF mRNA and its protein expression were significantly less than those of unlesioned contraletaral sides. Although a difference between week 6 and 12 was observed, the motoneurons were generally stable in the expression level of CNTF mRNA and its protein, and in the size and count after 12 weeks, with 78%, 84.4%, 80.9% and 83.7% respectively as compared with the unlesioned contralateral Amb. Conclusion: The results indicate that although degenerating changes occurre in the Amb motoneurons after long term laryngeal denervation, the ciliary neurotrophic factors activity of the lesioned motoneurons is still maintained at a certain level. [