The volatile oil from Acori Graminei Rhizoma downregulates NMDARs-ERK1/2-CREB signaling pathway to alleviate pain related emotions induced by inflammatory pain in rats

Objective

To investigate whether Acori Graminei Rhizoma (AGR) volatile oil can reduce inflammatory pain-induced pain-related mood in rats by downregulating NMDARs-ERK 1/2-CREB signaling pathway.

Methods

Thirty-six male SD rats were randomly divided into six groups: control group, sham group, complete Freund's adjuvant (CFA) group, CFA + 0.1 mL/10 g volatile oil group, CFA + 0.2 mL/10 g volatile oil group, and CFA + 0.4 mL/10 g volatile oil group. Six rats in each group were gavaged for 21 days and tested for mechanical pain hypersensitivity and positional avoidance (PEAP) before and after drug treatment. In addition, another batch of thirty-six male SD rats were randomly divided into six groups, including control, sham, CFA, CFA + saline, CFA + 0.1 mg/kg NMDA, and CFA + 0.1 mg/kg Ifenprodil groups. The control group did not receive any treatment, and the sham group received the same volume of sterile saline at the same site. Animals in each group were tested for mechanical pain hypersensitivity and positional avoidance before and after drug treatment. The expression levels of NMDAR1, NMDAR2A, NMDAR2A2B, mGlur1, ERK 1/2, CREB, and c-Fos in the basolateral amygdala (BLA) were determined by immunofluorescent staining and Western blot methods.

Results

AGR essential oil could reduce mechanical hyperalgesia and position avoidance in animals caused by CFA, and down-regulate NMDARs, mGlur1/5, ERK 1/2 and CREB expression. While up-regulation of c-Fos expression by NMDAR inhibitor Ifenprodil, reversed the above phenomena.

Conclusion

AGR essential oil alleviates inflammatory pain-induced pain-related mood in rats through downregulation of the NMDARs-ERK1/2-CREB signaling pathway.