[The expression of ciliary neurotrophic factor in facial nucleus after long-term facial denervation]

To explore the expression and distribution of Ciliary neurotrophic factor (CNTF) mRNA and its protein in the facial motoneuron in order to clarify its functional state after long-term facial denervation.

The facial nerves on the right sides were cut in dogs. Brain stems were removed and sectioned, and sections were separately used for histochemistry, immunohistochemistry and in situ hybridization of CNTF. The facial motoneurons were identified by Nissl staining. The count and intense of positive reactive motoneurons were measured by computer image processing system.

Transection of the facial nerve led to a very marked reduce in the count and intense of CNTF mRNA positive reactive motoneurons, and reached the minimal levels at week 3. CNTF immunoreactivity increased rapidly and reached the maximal levels at also 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 contralateral sides. Although a little difference between at week 12 and at 32 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 facial motoneurons.

The results indicated that although degenerating changes occurred in the facial motoneurons after long-term facial denervation, the ciliary neurotrophic factors activity of the lesioned motoneurons was still maintained at a certain level.