ABSTRACT
Aim To observe the effect of epidurally application of osthole on the model of nucleus pulposusinduced inflammatory radicular pain and the expression of p38 MAPK signaling related pathway in the spinal dorsal horn of rats.Methods The model of radicular pain was generated by putting nucleus pulposus to the L5 dorsal root ganglion (DRG).50％ MWT was measured using Von Frey filaments to calculate mechanical pain threshold before and after operation.50 μL of 20 g · L-1 osthole was administered epidurally in group Ost and 50 μL of 100 mL · L-1 DMSO in group DMSO at postoperative day (POD).The expression of phosphorylated p38 (p-p38),IL-18 and IL-18R in the lumbar spinal dorsal horn was detected by Western blot.IL-18 mRNA was assessed by real-time PCR.Results The mechanical pain threshold significantly decreased after operation (P ＜ 0.05),while the expression of protein p-p38 MAPK,IL-18,IL-18R and IL-18 mRNA was significantly different.Compared with DMSO group,50％ MWT was significantly increased and accompanied with the decrease of protein p-p38,IL-18,IL-lgR and IL-18 mRNA in Ost group after drug administration (P ＜ 0.05).The correlation analysis between protein concentration of p38 MAPK and IL-18 mRNA showed that the Spearman correlation coefficient was 0.9 (P ＜ 0.05).Conclusion p-p38 and IL-18 of spinal dorsal horn participate in the rat model with inflammatory radicular pain induced by nucleus pulposus,and IL-18R plays a role in maintenance of the pain.Osthole administered epidurally in the early stage of pain could alleviate the pain for a long time,which may be related with inhibiting p38 MAPK signaling related pathways.
ABSTRACT
Aim Toinvestigatetheanalgesiceffectsof epidural osthole application on the mechanical allodyn-ia and the ERK/MAPK signaling pathway and the expression of COX-2 mRNA in the spinal dorsal horn.Methods 125adultmaleSDratswererandomizedin-to five groups( n=25 each) :Blank, Sham, NP, Ost and vehicle. At postoperative day 6, 1mg/rat osthole 50 μl was injected epidurally into group Ost and the same volume of vehicle was given into group vehicle. The mechanical pain threshold was measured by 50%MWT at 1 day before operation and the 3 rd,6 th,7 th, 14 th,21 st day after operation. After the measurement of pain threshold on postoperative day 14 , the L4-6 segment of spinal dorsal horn was removed for determi-nation of the expression of ERK, pERK and COX-2 mRNAbyWesternblotandRT-PCR.Results Com-pared with blank group, the mechanical pain threshold was only down-regulated at day 1 after operation in sham group, the expression of pERK and COX-2 mR-NA in sham group showed no significant difference ( P>0. 05 ); the mechanical pain threshold was signifi-cantly down-regulated after operation in NP, Ost and vehicle groups( P0. 05). The correla-tion analysis on pERK1/2 and COX-2 mRNA revealed the Pearson correlation coefficient was 0 . 878 and 0 . 910 , suggesting a strong positive correlation between pERKandCOX-2mRNA.Conclusions Ostholead-ministrated in the early stage after surgery can alleviate the nucleus pulposus-induced radicular inflammatory pain probably by inhibiting the expression of pERK and COX-2 mRNA in spinal dorsal horn.