Material basis for inhibition of dragon's blood on capsaicin-induced TRPV1 receptor currents in rat dorsal root ganglion neurons

The effects of dragon's blood and its components cochinchinenin A, cochinchinenin B, loureirin B as well as various combinations of the three components on capsaicin-induced TRPV1 receptor currents were studied in acutely dissociated DRG neurons using both voltage and current whole-cell patch clamp technique. The results indicated that dragon's blood and its three components concentration-dependently reduce the peak amplitudes of capsaicin-induced TRPV1 receptor currents. There was no significant difference between the effects of dragon's blood and the combination wherein the three components were present in respective mass fractions in dragon's blood. The respective concentrations of the three components used alone were all higher than the total concentration of three components used in combination when the percentage inhibition of the peak amplitude was 50%. The proportion of three components was adjusted and the total concentration reduced, the resulting combination still inhibit the currents with a lower IC50 value, and inhibit capsaicin-induced membrane depolarization on current clamp. The combination of three components not only increase the capsaicin IC50 value, but also reduce the capsaicin maximal response. These result suggested that analgesic effect of dragon's blood may be partly explained on the basis of silencing pain signaling pathways caused by the inhibition of dragon's blood on capsaicin-induced TRPV1 receptor currents in DRG neurons and could be due to the synergistic effect of the three components. Antagonism of the capsaicin response by the combination of three components is not competitive. The analgesic effect of dragon's blood was also confirmed using animal models. (C) 2013 Published by Elsevier B.V.