Researching The Expression Of Nav1.8in Dorsal Root Ganglia When Intrathecal Injecting Fentanyl To Acute Inflammatory Visceral Pain Rats For Preemptive Analgesia

Objective:The preemptive analgesia effect of fentanyl intrathecal injected in different time points with the rat’s model of an acute inflammatory visceral pain. During measuring the writhing test scores and the mRNA and protein expression of Nav1.8, explore the effect of the acute inflammatory visceral pain and Nav1.8, besides expound the impact of fentanyl and Nav1.8under the preemptive analgesia.Methods:24male SD rats were randomly divided into4groups (n=6): normal control group(NS group), acetic acid group(AS group)> fentanyl before surgery group(FB group)and fentanyl in surgery group(FL group). After weighed, the rats were injected3.5%chloral hydrate intraperitoneally10ml/kg, blunt dissection rat L3, L4space, and the20G catheters were intrathecaled. Determine the rats3days after surgery, all rats with no symptom of nerver injury like lower limb dysfunction were inclued in the experment.The model of an acute inflammatory visceral pain was made by following way. NS group:rats received normal saline25μl by intrathecal injected and intraperitoneal injection. AS group:rats received normal saline25μl by intrathecal injected and0.6%acetic acid10ml/kg by intraperitoneal injection in5min. FB group:rats received fentanyl(0.05mg/ml)25μl by intrathecal injected and0.6%acetic acid10ml/kg by intraperitoneal injection in5min. FL group:rats received0.6%acetic acid10ml/kg by intraperitoneal injection and fentanyl(0.05mg/ml)25μl by intrathecal injected in30min. Observed and recorded behavior of each group’s response1h. After, all rats were anesthetized by3.5%chloral hydrate10ml/kg injected intraperitoneally, completed removal of rat L3-6DRG for detecting the mRNA and protein expression of Nav1.8by immunofluorescence, RT-PCR and Western-blot test.Results:Ethology:Compared with the AS group, the writhing test scores of FB group and FL group were lower(P<0.05). By contrast, the writhing test scores of FL group were higher(P<0.05) between FB group and FL group; Immunofluorescence:It revealed an apparent increase of Nav1.8in each group, especially in AS group(P<0.05). The level of increase in AS group higher than in FB group and FL group, and FB group was the least(P<0.05). RT-PCR and Western-blot test:Compared with NS group, the mRNA and protein expression of Nav1.8was increased in AS group, FB group and FL group(P<0.05); The level of increase in AS group higher than in FB group and FL group, and FB group was the least.Conclusions:Fentanyl intrathecal injected can relieve the acute inflammatory pain significantly in rat, and the preemptive analgesic effect is better, besides it is intensified to the inhibition on Nav1.8.