The Analgesic Effects And Mechanism Of Total Flavonoids Of Dragon’s Blood

Dragon’s blood which is one of the renowned traditional medicines can be used tostimulate circulation, relieve pain, control bleeding, aid the healing of sprains, etc. This studywas aimed to evaluate the analgesic effect of total flavonoids of Dragon’s blood (TFD) fromDracaena cochinchinensis (Lour.) S. C. Chen in animal models. The up-and-down procedurewas used to evaluate the acute oral toxicity of TFD. Whole-cell patch clamp technique wasused to study the effects of TFD on voltage-gated sodium channels and transient potentialvanilloid receptor1(TRPV1) in acutely dissociated rat dorsal root ganglion (DRG) neurons.In the formalin test, TFD (2-20mg/kg.i.p.) did not show any inhibition in the first phase,while TFD significantly inhibited the pain response of the second phase (15-30min). TFDsignificant reduced capsaicin-induced licking time in all doses (0.02~2mg per paw) tested inmice. The LD50of TDF in mice is greater than5g/kg by up-and-down procedure. TFDinhibited both TTX-s and TTX-r sodium currents in dose-dependent manner, and the half-maximalinhibitory concentrations of TFD for TTX-s and TTX-r sodium channels were (19.8±3.0)μg/mL and (36.3±4.6) μg/mL, respectively. Hill coefficient were0.85±0.12and1.03±0.15forthe TTX-r and TTX-s sodium channels, respectively. TFD could increase the half-maximalactivation voltage and reduce the half-maximal inactivation voltage for both TTX-s andTTX-r sodium channels. TFD inhibited1μM capsaicin activated current in DRG neurones. Itsmaximal inhibition efficiency was (50.6±2.2)%, half-maximal inhibitory concentration was(10.6±0.8) μg/mL, and Hill coefficient was1.94±0.24.These results indicated that the TFD have significant analgesic activity. TFD did notshow significant toxicity in acute oral toxicity test. Either voltage-gated sodium channelscurrent or capsaicin induced TRPV1current in DRG neurons could be inhibited by TFD.These results indicated that the mechanism of analgesic effect of TFD is that it modulateboth voltage-gated sodium channels and TRPV1receptor simultaneously in paintransmission pathways.