[Changes of trkB and trkC mRNA in facial nucleus after axotomy and end-to-end anastomosis in the rat].

OBJECTIVE

To explore the changes of receptor tyrosine kinase B and C (trkB and trkC) mRNA in facial motoneurons following facial nerve injury and repair.

METHODS

The time course of trkB and trkC mRNA in facial motoneurons following facial nerve transection and anastomosis was analyzed using in situ hybridization (ISH) and reverse transcriptase-polymerase chain reaction(RT-PCR) in adult rats.

RESULTS

In the facial nerve simple transection group, the intensity of trkB mRNA signal began to increase to 3d post-operation and to its maximum at 7d. Then, the intensity started to decrease at 14d, but it was still higher than that in the contralateral side at 35 d. After facial nerve injury, the changing trend of trkC mRNA was in the contrary to that of trkB. In the group of anastomosis, the changing trend of the intensity of trkB and trkC mRNA signal in the lesioned side was almost the same as that in the transection group. However, the intensity of trkB and trkC mRNA signal in the lesioned side returned to normal level at 35d. The finding obtained by RT-PCR was consistent with that of ISH. The statistic t-test showed significant differences between the two groups for the relative density level of positive band for trkB and trkC at 21d, 35d post-operation, respectively, (ttrkB,21 = 13.795, ttrkC,21 = 7.445, ttrkB,35 = 8.560, ttrkC,35 = 10.132, P < 0.01).

CONCLUSIONS

Transection of the facial nerve results in a upregulation of trkB mRNA, but a downregulation of trkC mRNA in axotomized facial motoneurons. The immediate anastomosis can't counteract and attenuate the changes of trkB and trkC induced by the nerve injury, but whether the changes of trkB and trkC return to normal level depends on the regeneration facial nerve.