Search Results (4)

This study aimed to investigate the glycaemic control potential and modulation of GABA-induced chloride currents (I_GABA) of H. revolutum and the possible bioactive xanthones. Fractions from the leaf and stem extracts (dichloromethane and methanol) were assessed for in vitro α-glucosidase-inhibitory potential and their ability to modulate I_GABA (GABAergic effect) through GABA_A receptors heterologously expressed in Xenopus oocytes. Xanthones 4-hydroxy-2,3-dimethoxy-9H-xanthen-9-one (1), 3-hydroxy-2,4-dimethoxy-9H-xanthen-9-one (2) and trans-3-(4-hydroxy-3-methoxyphenyl)-2-(hydroxymethyl)-5-methoxy-2,3-dihydro-7H-[1,4]dioxino[2,3-c]xanthen-7-one (3) were isolated from the stem and tested in the GABA_A receptors assay, but only 3 was assessed for α-glucosidase-inhibitory action. Compared to acarbose (IC₅₀ = 6.16 µM), 3 showed a mild to moderate α-glucosidase-inhibitory activity (IC₅₀ = 45.1 µM), which may be attributed to the absence of a hydroxyl group at its xanthone core. Isomeric compounds 1 and 2 significantly enhanced I_GABA with similar efficacy, while 3 was inactive, which may be attributed to its notable structural difference (cyclic ether substitution) compared to compounds 1 and 2. H. revolutum stem contains xanthones with α-glucosidase-inhibitory potential, which also enhance I_GABA and could be further studied as a medicinal plant for managing GABA_A receptor-mediated mental disorders and/or diabetes. Full article

iGABAR, a member of the Cys-loop ligand-gated ion channel superfamily, is a significant target of the insecticide ivermectin (IVM). GRD is the potential subunit of the insect iGABAR. However, little information about GRD in Ae. aegypti has been reported. In this study, we involved cloning and characterizing the iGABAR subunit GRD of Ae. aegypti (Ae-GRD). Sequence analysis indicated that Ae-GRD, as part of the cysteine-loop ligand-gated ion channel family, is similar to other insect GRD. RNA interference (RNAi) was employed to explore IVM resistance in Ae. aegypti, resulting in a significant reduction in Ae-GRD expression (p < 0.05), and the mortality of Ae. aegypti adults with Ae-GRD knockdown was significantly decreased after exposure to ivermectin. Bioinformatics prediction identified miR-71-5p as a potential regulator of Ae-GRD. In vitro, dual-luciferase reporter assays confirmed that Ae-GRD expression was regulated by miR-71-5p. Microinjection of miR-71-5p mimics upregulated miR-71-5p expression and downregulated Ae-GRD gene expression, reducing mortality by 34.52% following IVM treatment. Conversely, microinjection of a miR-71-5p inhibitor decreased miR-71-5p expression but did not affect the susceptibility to IVM despite increased Ae-GRD expression (p < 0.05). In conclusion, Ae-GRD, as one of the iGABA receptor subunits, is a potential target of ivermectin. It may influence ivermectin resistance by modulating the GABA signaling pathway. The inhibition of Ae-GRD expression by miR-71-5p decreased ivermectin resistance and consequently lowered the mortality rate of Ae. aegypti mosquitoes. This finding provides empirical evidence of the relationship between Ae-GRD and its miRNA in modulating insecticide resistance, offering novel perspectives for mosquito control strategies. Full article

Epipregnanolone (3β-hydroxy-5β-pregnan-20-one, Epi) is an endogenous steroid with important physiological effects and high affinity for GABA_A receptors. The effect of Epi on GABA-induced chloride current (I_GABA) in native neurons has hardly been studied. In this work, we studied the influence of Epi on the I_GABA in the Purkinje cells of rat cerebellum and pyramidal neurons of rat hippocampus with the patch clamp technique. We showed that Epi is a positive modulator of the I_GABA with EC₅₀ of 5.7 µM in Purkinje cells and 9.3 µM in hippocampal neurons. Epi-induced potentiation of the I_GABA was more potent at low vs. high GABA concentrations. Isopregnanolone (3β-hydroxy-5α-pregnan-20-one, Iso) counteracted Epi, reducing its potentiating effect by 2–2.3 times. Flumazenil, a nonsteroidal GABA_A receptor antagonist, does not affect the Epi-induced potentiation. Comparison of the potentiating effects of Epi and allopregnanolone (3α-hydroxy-5α-pregnan-20-one, ALLO) showed that ALLO is, at least, a four times more potent positive modulator than Epi. The combined application of ALLO and Epi showed that the effects of these two steroids are not additive. We conclude that Epi has a dual effect on the I_GABA increasing the current in the control solution and decreasing the stimulatory effect of ALLO. Full article

A new process for obtaining dibenzo[c,f][1,2,5]thiadiazepines (DBTDs) and their effects on GABA_A receptors of guinea pig myenteric neurons are described. Synthesis of DBTD derivatives began with two commercial aromatic compounds. An azide group was obtained after two sequential reactions, and the central ring was closed via a nitrene to obtain the tricyclic sulfonamides (DBTDs). Whole-cell recordings showed that DBTDs application did not affect the holding current but inhibited the currents induced by GABA (I_GABA), which are mediated by GABA_A receptors. These DBTDs effects reached their maximum 3 min after application and were: (i) reversible, (ii) concentration-dependent (with a rank order of potency of 2c = 2d > 2b), (iii) mediated by a non-competitive antagonism, and (iv) only observed when applied extracellularly. Picrotoxin (which binds in the channel mouth) and DBTDs effects were not modified when both substances were simultaneous applied. Our results indicate that DBTD acted on the extracellular domain of GABA_A channels but independent of the picrotoxin, benzodiazepine, and GABA binding sites. DBTDs used here could be the initial model for synthesizing new GABA_A receptor inhibitors with a potential to be used as antidotes for positive modulators of these receptors or to induce experimental epilepsy. Full article