OBJECTIVE Investigating the TrkC expression in the spared dorsal root ganglion (DRG) after acupuncture stimulation of spared root. METHODS Fifteen male adult cats were divided into three groups. Five cats were in the sham operation group; another five cats were subjected to unilateral root rhizotomy with (L1-L5, L7-S2 DRG sectioned, L6 DRG spared) and lived 7 days after operation; the last five cats were placed under electroneedle stimuli alternative at two groups of acupoints (including Tsusanli (St. 36) and Hsüanchung (G. B. 39), Fut'u (femur) (St. 32) and Sanyinchiao (Sp. 6) located in the distribution area of spinal nerve L6 on the operation side) 30 min a day for 7 days after unilateral root rhizotomy. On the 7th day, all animals were sacrificed. The L6 DRG from the experimental side of each animal was taken and made into frozen sections 20 microm in thickness. The sections were stained under the same condition using specific TrkC antibody (1:1000, Santa ) by immunohistochemistry ABC method. The number of TrkC immunoreaction (IR) neurons of DRG was observed and measured. RESULTS In L6 DRG of sham operated group, TrkC-IR was found mainly distributed in the cell plasm of some large sized neurons and a few medium and small sized neurons. Following partial dorsal root rhizotomy, the number of trKC-IR large sized neurons apparently decreased, while the number of the small and medium sized neurons markedly increased (P < 0.05). The number and reaction level of TrkC-IR large sized neurons apparently increased after acupuncture (P < 0.05), but the number of TrkC-IR small and medium sized neurons were not significantly changed. CONCLUSION This experimental study demonstrates that TrkC expression in L6 DRG neurons is upregulated after the acupuncture stimulation of spared root, suggesting that TrkC may be related to spinal plasticity.