Study On The Mechanism Of Antipruritus By Matrine

Background:Itch is a very uncomfortable sensation that elicits body to scratch repeatedly.Itching is not only common in patients with various skin diseases,but also common complications of some systemic diseases.Patients with pruritus are always feeling paroxysmal itch all over their body,leading to uncontrollable scratching,which seriously affects their work and life.So far the mechanism of pruritus remains unclear,lacking effective clinical drugs that can cure itch.Sophora flavescens,known as Kushen,is the dry root of Sophora Flavescens Ait with the functions of relieving heat,depriving the evil wetness,and killing parasites to relieve itch.Methanol extract of Kushen can significantly reduce 5-HT-induced scratching in mice.Kushen was used to treat pruritus with a long history,and the effect was significant.However,the anti-itch mechanism of Sophora flavescens was not clear.We selected matrine,the higher content of active alkaloids in Kushen,which had an inhibitory effect on chronic itch induced by ACD,suggesting the effects of relieving itch of matrine.However,the antipruritic mechanisms of matrine are not clear.Purpose:Study on the inhibitory effect of matrine on pruritus and explore the mechanism ofthetreatmentofprurituswithmatrine.Experimental methods:(1)Animal behavioral experiments were applied to study the antipruritic effects of matrine.(2)Primary cell culture and electrophysiological experiment were used to explore the effects of matrine on ion channels of DRG neurons,including voltage-gated channels sodium channels,potassium channels and calcium channels.(3)Calcium imaging assay was used to test the effect of matrine on singals induced by chloroquine and histamine.(4)MTT assay was used to study the effects of different concentration matrine on activity of DRG neurons and HEK293 cell lines.(5)The method of spinal cord slice electrophysiological recordings was used to study how matrine affected the synaptic transmission of spinal dorsal horn neurons.Results:(1)According to animal behavior experiments,it was found that matrine not only significantly inhibited the acute scratching response induced by histamine,chloroquine,and compound 48/80,but also the chronic itch behaviors induced by dry skin and atopic dermatitis.And this inhibition had the characteristic of concentration dependence(2)Electrophysiological experiments on DRG neurons indicated that matrine changed the excitability of DRG neurons,which showed that matrine inhibited sustained voltage gated potassium channel currents and the high voltage-activated N-type calcium channels,but did not affect voltage gated sodium channel currents.(3)The results of calcium imaging experiments showed that matrine could not inhibit the extracellular calcium influx what caused by chloroquine and histamine.(4)Matrine had no toxic effect on the activity of DRG neurons and HEK293 cell lines,that were testified by cytotoxicity-test.(5)Electrophysiological experiments in spinal cord slices showed that matrine inhibited the release of presynaptic membrane neurotransmitters from spinal dorsal horn neurons and did not affect the postsynaptic membrane receptors.Conclusion:Matrine significantly inhibited acute itching and chronic itching.One of its mechanisms is related to inhibition of high voltage activated N-type calcium channel on DRG neurons,thereby affecting the synaptic transmission of DRG neurons to the dorsal horn of the spinal cord.Significance:This study will provide a new way to clarify the mechanism of itch and the research of new antipruritic drugs.