The study of transport of neuro-trophin-3 in facial nerve

Objective: To study the transport of neuro-trophin-3 (NT-3) in facial nerve using radioactive tracer. Methods: After one of the two facial nerves of an adult rabbit was transected, a silicone chamber was inserted between the two stumps, and 7.4 MBq of 125I-NT-3 was administered into the chamber. At different time points after injection, radioactivities of both facial nerves and brain-stem were counted, respectively. 7.4 MBq of 131I-NT-3 or 131I-HSA was administered into the chambers of one group of two rabbits. 1 mg of NT-3 or 5.4 mg of HSA and 7.4 MBq of 131I-NT-3 were administered into the chambers of the another group of two rabbits. The eight rabbits were imaged at coronal section of head at different time points. Results: 4.05% of 125I-NT-3 was transported into facial nerve stumps from the chamber at 4 h after injection. The peak transport rate of 125I-NT-3 in facial nerve was shown at 12 h, the peak value was 27.04%. 12.16% and 41.18% of 125I-NT-3 were transported into brain-stem of experimental side at 12 h and 24 h, respectively. But, 131I-HSA was not transported in facial nerve. The transport of 131I-NT-3 was markedly restrained by NT-3 in facial nerve. Conclusion: NT-3 has a receptor-mediated axonal retrograde transport in facial nerve