Analgesia of Intrathecal Injection of Tanshinone IIA to Rats With Neuropathic Pain and Changes of CGRP Gene Expression Levels

This study aims to discuss analgesia of intrathecal injection of tanshinone IIA to rats with neuropathic pain and changes of calcitonin gene-related peptide (CGRP) gene expression levels. Thirty-six healthy male Sprague Dawley rats were selected and divided into the normal group (N), blank control group (B), and tanshinone IIA (IIA) by using a random number table group. Each group had 12 rats. The N group received no treatment. The B group was administered with intrathecal injection of normal saline, and the IIA group was given intrathecal injection of tanshinone IIA. Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of survival rats in different groups were tested. The cornu dorsal medullae spinalis of the L5 section of the rats that were killed were selected to test CGRP gene expression levels by reverse transcription polymerase chain reaction, CGRP positive cell rates of CGRP in tissues by immunohistochemical method, and CGRP protein expression levels in tissues by Western blot. MWT and TWL of the IIA and B groups after 1 and 2 weeks of treatment are significantly lower than those of group N (P < 0.05); however, those of the IIA group are higher than that of group B (P < 0.05). No significant differences are observed at any two moments in the N group (P > 0.05). However, significant differences are observed in the IIA group and B group at any two moments (P < 0.05). CGRP expression levels, positive cell rate, and protein relative expression of the IIA group and B group after 1 and 2 weeks of treatment are higher than those of the N group (P < 0.05). However, CGRP expression levels, positive cell rate, and protein relative expression of the IIA group are significantly lower than those of group B (P < 0.05). Intrathecal injection of tanshinone IIA has outstanding analgesia to rats with neuropathic pain. This condition is speculated to be related with inhibition of CGRP expression levels.