The Studies Of Chinese Buthus Martensi Karsch Polypeptides On The Sodium Channels Of Dorsal Root Ganglion Neurons

Part one:The purification,isolation and identification of Buthus martensi Karsch(BmK)neurotoxinsBmK2255 were purified and isolated from scorpion crude venom by classical chromatographic method.The amino acid sequence of BmK2255 determined by Edman degradation was found to be VRDGY IADDK NCAYF CGRNA YCDEE CIING AESGY CQQAG VYGNA CWCYK LPDKV PIRVS GECQQ.The MW of the component is 7223 Da.The amino acid sequence of BmK2255 is identical with Bukatoxin. Part two: Effects of Bukatoxin on tetrodotoxin-resistant(TTX-R) sodium channels in rat dorsal root ganglion neuronsThe effects of Bukatoxin on tetrodotoxin-resistant(TTX-R)sodium channels in rat dorsal root ganglion neurons were investigated by whole-cell patch clamp technique.The results revealed that about 18.72%,27.40%and 59.02%of peak TTX-R sodium currents were inhibited by Bukatoxin at the concertration of 20,40 and 80μg/ml respectively.Analysis of the effecs of the activation and inactivation kinetics of TTX-R sodium current by Bukatoxin showed:Bukatoxin shifed both the activation and inactivation curves.The activation curve of TTX-R sodium channel was slightly shifed in depolarizing direction by Bukatoxin and the inactivation curve was shifted in hyperpolarizing direction for about 6 inV.This promped that the opening time of TTX-R sodium channel was reduced thus resulting in the suppression of TTX-R sodium current.Part three:Effects of Bukatoxin on tetrodotoxin-sensitive(TTX-S) sodium channels in rat dorsal root ganglion neuronsThe effects of Bukatoxin on tetrodotoxin-sensitive(TTX-S)sodium channels in rat dorsal root ganglion neurons were investigated by whole-cell patch clamp technique.The results revealed that about 3.90%,10.10%and 30.98%of peak TTX-S sodium currents were increased by Bukatoxin at the concertration of 20,40 and 80μg/ml respectively. Analysis of the effecs of the activation and inactivation kinetics of TTX-S sodium current showed:Bukatoxin shifed both the activation and inactivation curves.The activation curve of TTX-S sodium channel was shifed in hyperpolarizing direction for about 9 mV by Bukatoxin and the inactivation curve was shifted in depolarizing direction for about 10 mV. This promped that the opening time of TTX-S sodium channel was prolonged thus resulting in the increase of TTX-S sodium current. Bukatoxin could slow the decay of TTX-S sodium current remarkably.