High-Dose Benzodiazepines Positively Modulate GABAA Receptors via a Flumazenil-Insensitive Mechanism.

Benzodiazepines (BZDs) produce versatile pharmacological actions through positive modulation of GABAA receptors (GABAARs). A previous study has demonstrated that high concentrations of diazepam potentiate GABA currents on the α1ß2γ2 and α1ß2 GABAARs in a flumazenil-insensitive manner. In this study, the high-concentration effects of BZDs and their sensitivity to flumazenil were determined on synaptic (α1ß2γ2, α2ß2γ2, α5ß2γ2) and extra-synaptic (α4ß2δ) GABAARs using the voltage-clamp electrophysiology technique. The in vivo evaluation of flumazenil-insensitive BZD effects was conducted in mice via the loss of righting reflex (LORR) test. Diazepam induced biphasic potentiation on the α1ß2γ2, α2ß2γ2 and α5ß2γ2 GABAARs, but did not affect the α4ß2δ receptor. In contrast to the nanomolar component of potentiation, the second potentiation elicited by micromolar diazepam was insensitive to flumazenil. Midazolam, clonazepam, and lorazepam at 200 µM exhibited similar flumazenil-insensitive effects on the α1ß2γ2, α2ß2γ2 and α5ß2γ2 receptors, whereas the potentiation induced by 200 µM zolpidem or triazolam was abolished by flumazenil. Both the GABAAR antagonist pentylenetetrazol and Fa173, a proposed transmembrane site antagonist, abolished the potentiation induced by 200 µM diazepam. Consistent with the in vitro results, flumazenil antagonized the zolpidem-induced LORR, but not that induced by diazepam or midazolam. Pentylenetetrazol and Fa173 antagonized the diazepam-induced LORR. These findings support the existence of non-classical BZD binding sites on certain GABAAR subtypes and indicate that the flumazenil-insensitive effects depend on the chemical structures of BZD ligands.

[Determination of common dyes in dyed safflower by near infrared spectroscopy].

Because the red and bright color of corolla is the main indicator for the quality assessment of good safflower,the dyed safflower is sometimes found at the herbal market,what is influence on this herb quality and efficacy. A total of 127 safflower samples was therefore collected from different cultivating areas and herbal markets in China to develop a rapid method to identify the dyed safflower. Near-infrared spectroscopy(NIRS) combined with characteristic identification,high performance liquid chromatography(HPLC),principal component analysis(PCA) and partial least squares regression analysis(PLS) were employed to differentiate safflower from dyed safflower samples,and further quantify the levels of the 6 dyes,i.e. tartrazine,carmine,sunset yellow,azorubine,acid red 73 and orange Ⅱ in the dyed safflower. The results indicated that the 50 safflower samples and 77 dyed safflower samples were located at different regions in PCA cluster diagram by NIR spectra. Tartrazine,carmineand and sunset yellow were found in the 77 dyed safflower samples with the amounts of 0. 60-3. 66,0. 11-1. 37,0. 10-0. 71 mg·g-1,respectively. It indicated that the three dyes were the common and main dyes in the dyed safflower. However,azorubine,acid red 73 and orange Ⅱ were not detected in all herb samples. A total of 62 dyed safflower samples were chosen as calibration samples to develop the model for estimating the amount of dyes in dyed safflower. The estimating accuracy was verified by another 15 dyed safflower samples. The values of tartrazine,carmine and sunset yellow in dyed safflower samples were compared between the NIRS and HPLC methods. Each value of mean absolute difference(MAD) was less than 5%. The correlation coefficients of tartrazine,carmineand and sunset yellow were 0. 970,0. 975,0. 971,respectively. It indicated the data quantified by NIRS and HPLC were consistence. It is concluded that NIRS can not only differentiate safflower from dyed safflower,but also quantify the amount of the dyes. NIRS is suitable for rapidly identify the quality of safflower.