Effect of sympathetic nerve on the expression of substance P mRNA in dorsal root ganglion of chronically compressed brachial plexus

Abstract

Objective To investigate the effect of different function of sympathetic nerve on the pain of peripheral nerve chronic compression. Methods Forty-eight male Sprague-Dawley rats were made into lower trunk chronic compression models and divided into 6 groups (A1,B1,C1,A2,B2,C2) with 8 rats per group. The C8T1 dorsal root ganglions of the compressed sides of group A1 (control group), B1 (sympathetic block group)and C1 (de-sympathetic group) were harvested 3 months after compression surgery. The compressed lower trunks of group A2 (control group), B2(sympathetic block group)and C2(de-sympathetic group)were decompressed 3 months after compression surgery and bred for another month and then the C8T1 dorsal root ganglions of the compressed sides were harvested. The levels of substance P mRNA in the C8T1 dorsal root ganglions were tested with RT-PCR technique. Results the mean relative levels of substance P mRNA of group A1, B1 and C1 were (3.620 ± 0.830) × 10-2, (2.945 ± 0.724) × 10-2, (2.239 ± 0.734) × 10-2, respectively, with a significant difference (P = 0.006) and those of group A2, B2 and C2 were (3.163 ± 1.026) × 10-2, (2.355 ± 0.680) × 10-2,(1.487 ± 0.802) × 10-2, the difference among which was statistically significant (P = 0.003). Conclusion The pain of peripheral nerve chronic compression is affected by sympathetic function. The more lower the sympathetic function is, the more light the pain is. Sympathetic blockage or resection helps to relieve the pain of peripheral nerve compression disease after being decompressed. Key words: Sympathetic nerve; Substance P; Chronic compression; Pain