Effect of dexmedetomidine pretreatment on inflammatory visceral pain in rats

Objective To investigate the effect of dexmedetomidine pretreatment on inflammatory visceral pain in rats. Methods Forty healthy male Wistar rats, weighing 200-300 g, aged 6-8 weeks, were divided into 5 groups (n=8 each) using a random number table method: control group (group C), visceral pain group (group VP), dexmedetomidine 1 μg/kg group (group Dex1), dexmedetomidine 5 μg/kg group (group Dex2) and dexmedetomidine 10 μg/kg group (group Dex3). The model of inflammatory visceral pain was established by intraperitoneally injecting 0.9% acetic acid 10 ml/kg in VP, Dex1, Dex2 and Dex3 groups, and the equal volume of normal saline was given instead in group C. At 15 min before intraperitoneal injection, dexmedetomidine 1, 5 and 10 μg/kg were injected via the tail vein in Dex1, Dex2 and Dex3 groups, respectively, and the equal volume of normal saline was given instead in C and VP groups.Behavioral changes of rats were observed within 60 min after the model was established, and visceral pain index (VPI) was calculated.Blood samples were collected from the hearts at 180 min after establishing the model for determination of tumor necrosis factor-alpha (TNF-α) concentrations in serum.The animals were then sacrificed, and colons were obtained for examination of pathological changes with a light microscope. Results Compared with group C, the VPI and serum TNF-α concentrations were significantly increased in VP and Dex1-2 groups, and the serum TNF-α concentrations were significantly increased (P 0.05). Compared with group VP, the VPI and serum TNF-α concentrations were significantly decreased (P<0.05), and the pathological changes of colon tissues were significantly attenuated in group Dex1-3.Compared with group Dex1, the VPI and serum TNF-α concentrations were significantly decreased (P<0.01), and the pathological changes of colon tissues were significantly attenuated in Dex2-3 groups.Compared with group Dex2, the VPI and serum TNF-α concentrations were significantly decreased (P<0.01), and the pathological changes of colon tissues were significantly attenuated in group Dex3. Conclusion Dexmedetomidine pretreatment can mitigate inflammatory visceral pain in rats. Key words: Dexmedetomidine; Visceral pain; Inflammation