Objective To study the transport of neurotrophin 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 125 I NT 3 was administered into the chamber At different time points after injection, ratioactivities of both facial nerves and brain stem were counted, respectively 7 4 MBq of 131 I NT 3 or 131 I 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 131 I 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 125 I NT 3 was transported into facial nerve stumps from the chamber at 4 h after injection The peak transport rate of 125 I NT 3 in facial nerve was shown at 12 h, the peak value was 27 04% 12 16% and 41 18% of 125 I NT 3 were transported into brain stem of experimental side at 12 h and 24 h,respectively But, 131 I HSA wasn't transported in facial nerve The transport of 131 I NT 3 was markedly restrained by NT 3 in facial nerve Conclusion NT 3 has a receptor mediated axonal retrograde transport in facial nerve