Analgesic effect of levo-corydalmine on neuropathic pain in rats and its mechanism

The aim of the present study was to investigate the effects of levo-corydalmine(l-CDL)on chronic constrictive injury(CCI)-induced neuropathic pain and central sensitization in spinal cord. The mechanical withdrawal threshold in rats was assessed by Von-Frey fibers and the thermal withdrawal latency was assessed by thermal stimulus apparatus. The level of phosphorylated N-methyl-D-aspartic acid receptor 1(NR1)in L4-L6 spinal cord was analyzed by immunoblotting and the expression of calcitonin gene related peptide(CGRP)and c-fos in spinal cord dorsal horn were analyzed by immunofluorescence. Results showed that l-CDL(7. 5, 15, 30 mg/kg, ig)inhibited CCI-induced mechanical allodynia and thermal hyperalgesia in a dose-dependent manner. l-CDL significantly inhibited the up-regulation of p-NR1, c-fos and CGRP in CCI rats without tolerance. In conclusion, l-CDL has a good relieving effect on central sensitization in spinal cord, thus generating outstanding analgesic activity on CCI-induced neuropathic pain.