Effects Of Dexmedetomidine On The Expression Of Voltage-gated Sodium Channel Nav1.8 In The Dorsal Root Ganglion Of Rats With Acute Visceral Pain

Objective:To investigate the effect of dexmetomidine on acute visceral pain in rats with the expression of voltage-gated sodium channel Nav1.8 in the DRG.Methods:32 healthy adult male SD rats weighing 180~220 g were randomly divided into 4 groups(n=8): control group(group CK),acute visceral pain model group(group VP),dexmedetomidine group(group Dex),dexmedetomidine+atipamezole group(group Dex A).Rats in the group VP,group Dex,and group Dex A were injected with rectal injection of capsaicin at a dose of 10-3 mmol/L to establish the acute visceral pain model.In the group CK,equal volume saline was injected into rectum.Before 20 min of model establishment,rats of group Dex A were injected with 1 mg/kg of atipamezole subcutaneously through the back of the neck.At 15 min before model establishment,group Dex and Dex A rats were injected with dexmedetomidine 10 μg/kg through the tail vein respectively.The remaining groups were injected subcutaneous and/or caudal veins with equal volumes of saline at the same time.Observed and recorded the visceral pain behavior score for 1 hour after the establishment of visceral pain model in each group of rats;At the end of the behavioral scoring,the L3-L6 DRG was taken and observed the number of Nav1.8-expressing cells in DRG small-diameter C-fiber neurons by immunohistochemistry.The q RT-PCR method was used to detect the relative expression of Nav1.8 m RNA.Results:Compared with the group CK,the visceral behavior scores,the number of Nav1.8 positive cells and the relative expression of Nav1.8 m RNA in group VP,group Dex,and group Dex A significantly increased(P<0.05).Compared with the group VP,the visceral behavior score,the number of Nav1.8 positive cells and the relative expression of Nav1.8 m RNA in the group Dex were significantly decreased(P<0.05).Compared with the group Dex,the visceral pain behavior score,the number of Nav1.8 positive cells and the relative expression of Nav1.8 m RNA in DRG small-diameter C-fiber neurons in group Dex A were significantly higher(P<0.05).Conclusion:Intravenous injection of dexmedetomidine will inhibit the number of Nav1.8 positive cells and the relative expression of Nav1.8 m RNA in DRG small-diameter C-fiber neurons,and reduce the acute visceral pain induced by capsaicin in rats.