Abstract
This study tested the hypothesis that combination therapy using extracorporeal shock wave (ECSW)-melatonin (Mel) was superior to either alone at ameliorating neuropathic pain (NP). NP was induced by chronic constriction injury (CCI) to the left sciatic nerve in rats. Animals were categorized into sham control (group 1), CCI only (group 2), CCI-ECSW (group 3), CCI-Mel (group 4) and CCI-ECSW-Mel (group 5). By days 2 and 8 after CCI, the mechanical paw withdrawal threshold (MPWT)/thermal paw withdrawal latency (TPWL) were highest in group 2, lowest in group 1, significantly lower in group 5 than in groups 3 and 4 (all p<0.0001), and not significantly different between groups 3 and 4. The protein expressions of inflammatory (TNF-α/NF-κB/MMP-9/IL-1ß/GFAP/ox42), oxidative-stress (NOX-1/NOX-2/NOX-4/oxidized protein), DNA/mitochondrial-damaged (γ-H2AX/cytosolic mitochondria), apoptotic (cleaved capase-3/PARP), and MAPK family biomarkers (p-P38/p-JNK/p-ERK1/2) in dorsal root ganglia and spinal dorsal horn expressed a similar pattern of MPWT/TPWL among the five groups, except for significantly higher in group 4 than in group 3 (all p<0.0001). The protein expressions of Nav.1.3, Nav.1.8 and Nav.1.9 in sciatic nerve displayed an identical pattern to inflammation among the five groups (all p<0.001). Pain facilitated cellular expressions (p-P38+/peripherin+ cells, P38+/NF200+ cells) displayed an identical pattern to inflammation among the five groups (all p<0.0001). In conclusion, ECSW-Mel combination therapy markedly ameliorated NP induced by CCI.