OBJECTIVE To investigate the change of c-jun expression in spared dorsal root ganglion (DRG) following partial dorsal root rhizotomy and acupuncture. METHODS Fifteen adult cats were divided into three groups with five cats in every group--sham operation, operation, and acupuncture following operation respectively. Animals of operation group were subjected to unilateral root rhizotomy (L1-L5, L7-S2 DRGs were sectioned, L6 DRG was spared). Electro-needling was performed alternatively at two sets of acupoints, including Zusanli and Xuanzhong, Futu and Sanyinjiao, located in the distribution area of spinal nerve L6 on the operated side, 30 min everyday for 7 days following unilateral root rhizotomy. The animals of sham operation group experienced only skin and muscle incisions. On the 7th day after operation, all animals were sacrificed. The L6 DRG on the disposal side of each animal was taken and made into frozen sections 20 micrograms in thickness. The sections were stained under the same condition using specific c-jun antibody (1:1000, Santa Cruz) by immunohistochemistry ABC method. The distribution and number as well as immunoreactive level of c-jun positive neurons in DRG were observed and measured. RESULTS In the L6 DRG of sham operation group, only parts of neurons were stained. In contrast, the number of positive neurons and immunoreactive level for c-jun increased significantly in operation group (P < 0.05). Compared with the operation group, the operation plus acupuncture group had higher c-jun immunoreactive level of neurouns, but its number of c-jun positive neurons didn't change markedly. CONCLUSIONS Partial dorsal root rhizotomy leads to the up-regulation of c-jun expression in neurons of spared DRG, and acupuncture enhances the up-regulation.