Effects of hydrogen-rich saline on chronic inflammatory pain in rats / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the effects of hydrogen-rich saline on chronic inflammatory pain in rats.Methods Thirty-two male Sprague-Dawley rats,aged 8-10 weeks,weighing 200-250 g,were randomly divided into 4 groups (n =8 each) using a random number tablecontrol group (group C);complete Freund's adjuvant (CFA) group;hydrogen-rich saline group (group H2);CFA + hydrogenrich saline group (CFA+H2 group).Chronic inflammatory pain was induced by injecting CFA 100 μl into the plantar surface of the left hindpaw in CFA and CFA + H2 groups.In H2 and CFA + H2 groups,0.6 mmol/L hydrogen-rich saline 5 ml/kg was injected intraperitoneally once a day for 7 consecutive days starting from 1 day after injection of CFA,while the equal volume of normal salinc was given instead of hydrogen-rich saline in C and CFA groups.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 1 day before CFA injection and 1,3 and 7 days after CFA injection.The rats were sacrificed after the last measurement of pain threshold on day 7 after CFA injection.The left lumbar segments (L4 5) of the spinal cord were removed for determination of nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expression by Western blot.Results Compared with C group,no significant change was found in the MWT,TWL and expression of Nrf2 and HO-1 in H2 group,and the MWT was significantly decreased,the TWL was shortened,and the expression of Nrf2 and HO-1 was up-regulated in CFA and CFA+H2 groups.Compared with CFA group,the MWT was significantly increased,the TWL was prolonged,and the expression of Nrf2 and HO-1 was up-regulated in CFA+H2 group.Conclusion Hydrogen-rich saline can alleviate chronic inflammatory pain in rats,and activation of Nrf2/ARE signaling pathway in the spinal cord is involved in the mechanism.