Effect of polydatin on neuropathic pain in rats

Abstract

Objective To evaluate the effect of polydatin on neuropathic pain in rats. Methods Forty male Sprague-Dawley rats, aged 6-8 weeks, weighing 200-230 g, were randomly divided into 5 groups (n=8 each)using a random number table: sham operation group (group S), neuropathic pain group (group NP), polydatin 5 mg/kg group (group P1), polydatin 10 mg/kg group (group P2), and polydatin 20 mg/kg group (group P3). Neuropathic pain was induced by chronic constriction injury in NP and P1-3 groups.In group S, the sciatic nerve was only exposed but not ligated.In S and NP groups, normal saline 0.1 ml was injected intraperitoneally immediately after operation and at 1, 3, 5 and 7 days after operation (T1-4). In P1-3 groups, polydatin 5, 10 and 20 mg/kg (in normal saline 0.1 ml)were injected intraperitoneally immediately after operation and at T1-4.At 1 day before operation (T0)and T1-4, the mechanical paw withdrawal threshold (MWT)and thermal paw withdrawal latency (TWL)were measured.After measurement of pain threshold at T4, the rats were sacrificed, and L4-6 segments of the spinal cords were removed for determination of the expression of high-mobility group box 1 (HMGB1), Toll-like receptor 4 (TLR4), interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α)and monocyte chemotactic protein-1 (MCP-1)by Western blot. Results Compared with group S, the MWT was significantly decreased, and the TWL was significantly shortened at T1-4 in group NP, the MWT was significantly decreased at T1-4, and the TWL was significantly shortened at T2-4 in group P1, the MWT was significantly decreased at T1-4, and the TWL was significantly shortened at T3, 4 in group P2, the MWT was significantly decreased at T1-4 in group P3, and the expression of HMGB1, TLR4, IL-1β, TNF-α and MCP-1 was significantly up-regulated in NP, P1 and P2 groups (P 0.05). Compared with group P1, the MWT was significantly increased at T4 in group P2, and the MWT was significantly increased at T1-4, the TWL was significantly prolonged at T3, 4, and the expression of HMGB1, TLR4, IL-1β, TNF-α and MCP-1 was significantly down-regulated in group P3 (P<0.05). Compared with group P2, the MWT was significantly increased at T3, 4, and the expression of TLR4, IL-1β, TNF-α and MCP-1 was significantly down-regulated in group P3 (P<0.05). Conclusion Polydatin can alleviate neuropathic pain through inhibiting inflammatory responses in the spinal cord of rats. Key words: Polygonum cuspidatum; Neuralgia