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已知黃苓水抽提物具有鎮靜作用，對小鼠大腦皮質GABAA接受器之benzeokiazdpam(BDZ)結合處有很強親和力，其Ki值為l0.5μg/ml。本研究中，藉由高效率液相層析術(HPLC)與接受器結合實驗評估，證實黃苓水抽提物中作用在BDZ結合處之主要成分，並不是黃苓甘(baicalin)、泛黃苓素(wogonin)或chtysin。在整體動物實驗中，黃苓水抽提物並不能抑制penyleneterazol(85mg/Kg，S.C.)所誘發之陣攣性痙攣，但可抑制最大電擊刺激所引發的強直性痙攣，其一半有效劑量(ED50)為3.6g/Kg，此結果和已知BDZ作用劑可對抗二種痙攣之作用不同，暗示黃苓水抽提物並不是BDZ致效劑的藥物。已知GABA可作用在GABAA接受器，而打開氯離子通道(C1-chanel)，所以利用放射性標定氯離子(36C1-)為追蹤劑，來評估藥物對GABAA接受器氯離子通道之活性。實驗結果顯示，黃苓水抽提物並不會影響GABA增加氯離子之通透量，證實黃苓水抽提物不具BDZ作用劑之作用。
藉由GPLC定量分析，得知黃苓水抽提物中含有黃苓甘5.9%、泛黃苓素0.2%、chrysin0.005%，對此三化合物做相似之藥理評估顯示，黃苓甘對BDZ結合處並無明顯親和力，對GABA增加氯離子通透量亦沒有影響;而泛黃苓素雖可作用在BDZ結合處(Ki=2.4μM)，但其對氯離子通透量改變在統計上並沒有意義，顯示泛黃苓素可能為BDZ之拮抗劑。Chrysin可作用在BDZ結合處，在小鼠大腦皮質之Ki值為75μM，並且依濃度的增加，對GABA促進氯離子通透量亦增加，顯示其為BDZ之作用劑。
綜合上述，本研究探討黃苓水抽提物作用在BDZ接受器之成分，證實其不是黃苓甘、泛黃苓素及chrysin。黃苓水抽提物雖有抗痙攣 之作用，但其機轉可能不是經由活化GABA接受器之BDZ結合處;在氯離子通透性之實驗亦證實其不是BDZ結合處之作用劑。黃苓甘不與BDZ結合處結合;泛黃苓素為BDZ拮抗劑;而在黃苓水抽提物中含有微量chrysin，其為BDZ作用劑，與文獻報導吻合。
The water extract of Chinese herbal drug Huangqin (RadixScutellariae) had sedative effect and had high affinity for the benzodiazepine (BDZ) binding site of GABAA receptors with a Ki value of 10.5 μg/ml. Using HPLC separation and receptor binding assay, the present study demonstrated that the principle in the water extract of Huangqin (WEH) acted on the BDZ binding site was not baicalin, wogonin or chrysin. In vivo study, WEH had no significant effect on pentylenetetrazol-induced clonic seizures in mice, although it could inhibitmaximal electroshock-induced tonic seizures with an ED50 of 3.6g/Kg. This anticonvulsion effect of WEH was different from that of BDZ agonist which has anticonvulsant activity on both seizures. This result suggested that WEH was not a BDZ agonist.
To study the Cl' channel activity of GABAA receptors, the 36C1- was used as a tracer. GABA acts on the GABAA receptor to open the C1- channel and increases the amount of C1- uptake. By this assay, WEH had no significant effect on GABA-stimulated C1- uptake, further comfirming that WEH is not a BDZ agonist.
Using HPLC, WHE was analyzed to contained 5.9 % balcalm, 0.2 % wogonin, and 0.005 % chrysin. Therefore, these 3 compounds were evaluated with the same assays. Baicalin had no affinity for BDZ receptors, and had no effect on GABA-stimulated C1- uptake. Wogonin interacted with the BDZ receptors with a Ki of 2.4 μM in cortex, but had no siginificant effect on GABA-stimulated C1- uptake. This result suggested that wogonin was a BDZ antagonist. Chrysin interacted with BDZ receptor with a Ki of 7.5 μM in cortex, and also increased the GABA-stimulated C1- uptake in a concentration dependent manner, indicating that chrysin was a BDZ agonist.
In summary, the present study investigated the principle of WEH acting on the BDZ receptor and showed that this principle was not baicalin, wogonin, or chrysin. The anticonvulsant activity of WEH was demonstrated and was not via an activation on the BDZ binding site of GABAA receptors. The latter was further comfirmed by C1- uptake assay. Baicalin had no interaction with the BDZ binding sites, whereas wogonin was a BDZ antagonist. WEH only contained small amount of chrysin, but in consistent with the literature chrysin was a BDZ agonist.
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