| [Objective] To explore effects of partial dorsal rhizotomy and electro-acupuncture (EA) on the expression of SP in lumbar II of the spinal cord (L1,L3, L5, L7) in cats so as to find out the relationship between SP expression and EA promoting spinal cord plasticity.[Methods] 20 adult healthy male cats were divided randomly into 4 groups (n=5 in each group): normal control group; bilateral partial dorsal root rhizotomy 14th day, 1 month and 3 month groups (bilateral L1-L5, L7-S2 DRGs were transected; but the L6 DRG was spared) and received left EA treatment after operation (at acupoints Zusanli and Xuanzhong, Futu and Sanyinjiao, were stimulated alternately at the frequency of 98 HZ for 30 minutes every day. They were allowed to survive 14 day, 1 month and 3 months after operation). The cats in different groups were perfused and L1,L3,L5,L7 spinal segments were collected and were cut into 20μm frozen sections. Then, the sections were stained with specific SP (1:5000) antibody by the immunohistochemistry two-step method under the same condition. The distribution and the number of SP positive varicosity in lumbar II of the spinal cord (L1,L3, L5, L7) were observed and counted. All data were analyzed by One-Way ANOVA and Independent-Samples t-test.[Results] 1. SP immunopositive varicosity mainly dispersed in superficial lamina of dorsal horn in spinal cord with the form of particles. 2. At 14 days after partial removal of dorsal root ganglia and EA, the number of SP immunopositive varicosities decreased in lamina II of L1, L3, L5, L7 spinal segments and reached the lowest at 1 month. At 3 months after operation, the number of these varicosities increased to different extents: equal to the level of 14 day in L1 and L3 spinal segments while surpassed it in L5 and L7 segments, but still less than the normal level. And there were less SP positive staining varicosities in the unilateral spinal cord receiving acupuncture than the other lateral (P<0.05).[Conclusion] The partial removal of dorsal root ganglia lead to the change in the number of SP positive staining varicosities: first decreased and subsequently increased. This suggested that SP positive varicosities derived from spared dorsal root ganglion sprouted in the spinal cord and promoted spinal cord plasticity in rats subjected to partial dorsal root ganglionectomies.Comparing with the operated group, the number of SP positive varicosities derived from spared dorsal root ganglion significantly decreased after EA. This suggested that EA releasing pain might have a relation with decrease of SP.
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