Aconiti Brachypodi
Radix, belonging to the genus of
Aconitum
(Family Ranunculaceae), are used clinically as
anti-rheumatic, anti-inflammatory and anti-nociceptive in traditional medicine of China. However, its mechanism and
influence on nociceptive threshold are unknown and need further investigation. The analgesic effects of ethanolic extract of
Aconiti Brachypodi Radix (EABR) were thus studied
in vivo and
in vitro. Three pain models in mice were used to assess the
effect of EABR on nociceptive threshold.
In vitro study was conducted to clarify the modulation of the extract on the
tetrodotoxin-sensitive (TTX-S) sodium currents in rat’s dorsal root ganglion (DRG) neurons using whole-cell patch clamp
technique. The results showed that EABR (5-20 mg/kg, i.g.) could produce dose-dependent analgesic effect on hot-plate tests
as well as writhing response induced by acetic acid. In addition, administration of 2.5-10 mg/kg EABR (i.g.) caused
significant decrease in pain responses in the first and second phases of formalin test without altering the PGE
2 production in
the hind paw of the mice. Moreover, EABR (10 μg/ml -1 mg/ml) could suppress TTX-S voltage-gated sodium currents in a
dose-dependent way, indicating the underlying electrophysiological mechanism of the analgesic effect of the folk plant
medicine. Collectively, our results indicated that EABR has analgesic property in three pain models and useful influence on
TTX-S sodium currents in DRG neurons, suggesting that the interference with pain messages caused by the modulation of
EABR on TTX-S sodium currents in DRG neurones may explain some of its analgesic effect.
