Transient receptor potential vanilloid 1 involved in the analgesic effects of total flavonoids extracted from Longxuejie ().

Abstract

<h4>Objective</h4>To evaluate the analgesic effects of total flavonoids of Longxuejie (<i>Resina Dracaenae Cochinchinensis</i>) (TFDB) and explore the possible analgesic mechanism associated with transient receptor potential vanilloid 1 (TRPV1).<h4>Methods</h4>Whole-cell patch clamp technique was used to observe the effects of TFDB on capsaicin-induced TRPV1 currents. Rat experiments <i>in vivo</i> were used to observe the analgesic effects of TFDB. Western blot and immunofluorescence experiments were used to test the change of TRPV1 expression in DRG neurons induced by TFDB.<h4>Results</h4>Results showed that TFDB inhibited capsaicin-induced TRPV1 receptor currents in acutely isolated dorsal root ganglion (DRG) neurons of rats and the half inhibitory concentration was (16.7 ± 1.6) mg/L. TFDB (2-20 mg/kg) showed analgesic activity in the phase Ⅱ of formalin test and (0.02-2 mg per paw) reduced capsaicin-induced licking times of rats. TFDB (20 mg/kg) was fully efficacious on complete Freund's adjuvant (CFA)-induced inflammatory thermal hyperalgesia and capsaicin could weaken the analgesic effects. The level of TRPV1 expressions of DRG neurons was also decreased in TFDB-treated CFA-inflammatory pain rats.<h4>Conclusion</h4>All these results indicated that the analgesic effect of TFDB may contribute to their modulations on both function and expression of TRPV1 channels in DRG neurons.