Gastrodin Alleviated Chemotherapy-induced Neuropathic Pain By Enhancing Na_v1.7 And Na_v1.8 Channel Inactivation And Regulating The Excitability Of Dorsal Root Ganglion Neuron

Objective:Animal models have provided useful insights into the development and treatment of neuropathic pain.There is substantial evidence for gastrodin（GAS）,an active component derived from the chinese herb Gastrodia elata Blume,on chemotherapy-induced neuropathic pain（CINP）of rats.Lots of human genetic studies show that Na_v1.7 and Na_v1.8 are key moleculars determinant of pain.The purpose of study is to investigate whether and how GAS modulates electrical excitability in nociceptive dorsal root ganglion（DRG）neurons,and modulates the expressions and properties of Na_v1.7 and Na_v1.8,thus participates in the pathogenesis in chemotherapy-induced peripheral neuropathy,and influence the dynamic process of inactivation.Furthermore,we test the expression of SCN9A and SCN10A,which can help us learning the function of GAS in-deeps.Method:Vincristin was administered by gavaged with alternate days until five injections,after the model of vincristin-induced neuropathic pain was successfully,and then GAS was administered by gavaged with every day.Heat hyperalgesia and mechanical threshold were measured by using electronic heating platen instrument.Voltage-gate Na+channels regulate neuron excitability by upstroke of action potentials.Generally,Na_v1.7 sodium channels and Na_v1.8 sodium channels are essential composed of normal function of sensory neurons.Using current patch clamp recording technique to explore how GAS regulate the function of action potential in DRG cells and model DRG cells.Thirdly,we performed whole-cell patch clamp recording technique to investigate how GAS influence the inward current of Na_v1.7sodium channel and Na_v1.8 sodium channel.At the same time,exploring GAS how to influence the dynamic process of inactivation.HEK293 cells stably expressing Na_v1.7 to determine the effects of GAS on Na_v1.7 in vivo.Using q-PCR method find the influncen in SCN9A and SCN10A induced by GAS on CINP rats.Result:Using vincristine-induced Neuropathic Pain model,we found that compared to model group,thermalgesia threshold of GAS 120mg/kg group rats exhibited significantly lower thermal painful stimulus.Thermalgesia threshold of GAS 60mg/kg group rats and GAS 120mg/kg group rats were significantly lower than model of vincristin-induced neuropathic pain.GAS showed decreased firing frequency of neurons.GAS60mg/kg and 120mg/kg can increase mechnical threshold in model rats（P>0.05）.Decreased excitability of action potential by significantly decreased the peak amplitude,the number of AP and increase the rheobase and width compared with control group in model DRG neurons.Decreased excitability of action potential by significantly decreased the peak amplitude,the number of AP an the upstroke slope and increase width compared with control group in normal DRG neurons.Nav1.8 and inactive current dynamics process affected by GAS was significantly shift to decreases.GAS caused dramatic hyperpolarizing shift of Nav1.8 channel inactivation.When the HEK293B cells expressing Nav1.7 channels were hold at-90 mv,the IC₅₀ values were16.2μmol/L.GAS caused dramatic hyperpolarizing shift of channel inactivation.After the CINP animal model was built,the level of SCN9A and SCN10A in DRG was improved obviously with the time prolonged to 14 days,which was statistically significant（P<0.01）.The expression level of treat by GAS in DRG was declined compared to the model group.Conclusions:Our results demonstrate that GAS is a regulator of Na_v1.7channel and Na_v1.8 channel by enhancing inactivation to regulate modulates excitability of the somatosensory nociceptive neurons and decreased expression of SCN9A and SCN10A participates in the process of neuropathic pain.