| The Dai medicine Dragon's blood is a traditional medicine, which has the effectiveness of blood circulation, and also plays a role in hemostasis convergence, especially plays significantly analgesic and anti-inflammatory role in the extensive clinical application. In recent years, the experimental group have done many studies about the analgesic mechanism of Dragon's blood, the research of Dragon's Blood on the TTX-S and TTX-R sodium channel current and capsaicin receptor current have done in rat primary sensory neurons (including DRG and TG neurons) by patch-clamp technique. In addition, through extracellular microelectrode recording technique, we studied the effect of Dragon's Blood and its components on rat spinal dorsal horn neurons evoked discharge. The results of these studies illustrated the Dragon's blood modulate the pain information in the central from different levels and different mechanisms, thus making the analgesic effect. The results of Dragon's Blood modulate the sodium channels in DRG cells and inhibit evoked discharge frequency in rat spinal dorsal horn neurons showed that Dragon's Blood modulate pain information through central and peripheral, but lack of some relative study on its analgesic activity type . The study done before proposed the Dragon's Blood through the interference of pain transmission to play its analgesic effect, while one branch of the DRG cell body axons connect with peripheral sciatic nerve, if we have done some corresponding researches on sciatic nerve, Dragon's Blood blocking the nerve conduction would be more convincing.Firstly, a series of pharmacological experiments were carried out on mice, mainly on hot plate, tail flick test and writhing test, to determine the type of analgesic activity about Dragon's Blood, through experiments we found that in hot plate and tail flick test experiments 0.5g / L Dragon's Blood could significantly prolong the Licking latency and tail flick latency; in the writhing test, writhing number within 15min could significantly reduced. The results show that Dragon's Blood not only has good central analgesic activity, but also has good peripheral analgesic activity.Secondly, to verify the pharmacological mechanism of the Dragon's Blood's analgesic effect, we will make bullfrog sciatic nerve specimens to observe the effect of Dragon's Blood on the sciatic nerve action potential. Experiments showed that 0.5g / L Dragon's Blood made the action potential amplitude of bullfrog sciatic nerve decrease, neural excitability refractory period extended and excitability conduction velocity slowed down, these results further confirmed the function of Dragon's Blood block nerve conduction, and further confirmed the intervention effect of Dragon's Blood on pain transmission.Furthermore, in patch-clamp studies, Dragon's Blood and its main components can modulate both the capsaicin receptor and sodium channels which are closely related to the pain transmission. According to existing literature, capsaicin can modulate voltage-gated sodium channels, inhibit sodium current, and this modulation is associating with the capsaicin receptor. Because of the fact that Loureirin B has a similar chemical structure to capsaicin, and it could also inhibit the sodium channel current, we speculate that the effect of Loureirin B on the sodium channel current is also probably relate to the capsaicin receptor. Clarifying these issues would make the results obtained more useful. Based on the above analysis, we designed patch clamp experiments to make further study on analgesic mechanism of Dragon's Blood and its components -Loureirin B in this paper.Based on the similarity of the modulation of Loureirin B on capsaicin receptor and sodium channels as capsaicin does, we finally adopt the whole-cell patch-clamp technique to study the Loureirin B modulation of voltage-gated sodium channels and its relationship with capsaicin receptors in DRG cells, and to explore the interaction between capsaicin and Loureirin B. We can obtain these following results :1,When Loureirin B and capsaicin are combined, the inhibition rate of their combined effect on sodium channel currents is higher than they used respectively; 2,When Loureirin B and capsaicin are combined , while fix the concentration of one drug and change the other, the extent of activation curve shift to the depolarization direction and the extent of accelerate the sodium channel inactivation would increase as the concentration of latter drug decreases; 3,Through the analysis of drug interactions we can obtain the fact that Loureirin B and capsaicin has antagonistic effects when modulate the sodium channel. The results also show that the modulation of Loureirin B on sodium channels has some relation with capsaicin receptor indeed.The findings of this paper can be used as the foundation to research new mechanism of the analgesic effect of Dragon's Blood, combined with the analgesic studies about Dragon's Blood before, making us able to conduct in-depth Dragon's Blood pharmacological research, and develop new analgesic drugs in the near future, also benefit the second development of Dragon's blood as well, improving their scientific and technological content and expanding social and economic benefits. |
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