Anxiolytic activity of ferulic acid in the light-dark test in zebrafish

The anxiety disorders belong to a group of mental disorders in which the patients present excessive fear and worry. Studies with ferulic acid have shown positive results on treating depressive symptoms. As many antidepressive drugs are effective in treating anxiety, the objective of the present study was to evaluate ferulic acid’s anxiolytic activity and possible mechanism of action in the light-dark test in zebrafish. To evaluate anxiolytic activity, the light-dark preference test was performed after exposure of the animals to ferulic acid or positive control (clonazepam or fluoxetine). Ferulic acid increased the time spent in the clear compartment at concentrations of 250 and 500 mg/L, not differing from the groups exposed to clonazepam or fluoxetine. To evaluate the possible mechanism of action, pre-exposure to flumazenil was carried out, followed by exposure to ferulic acid or positive control, with subsequent testing. Pre-exposure to flumazenil caused a significant reduction in the time spent in the clear compartment of ferulic acid and clonazepam groups but did not alter the effect of exposure to fluoxetine. These results suggest that ferulic acid promotes an anxiolytic effect, possibly through an action at the benzodiazepine binding site at the GABAA receptor.

Competitive Antagonism of Etomidate Action by Diazepam

Background Recent cryo-electron microscopic imaging studies have shown that in addition to binding to the classical extracellular benzodiazepine binding site of the α1β3γ2L γ-aminobutyric acid type A (GABAA) receptor, diazepam also binds to etomidate binding sites located in the transmembrane receptor domain. Because such binding is characterized by low modulatory efficacy, the authors hypothesized that diazepam would act in vitro and in vivo as a competitive etomidate antagonist. Methods The concentration-dependent actions of diazepam on 20 µM etomidate-activated and 6 µM GABA-activated currents were defined (in the absence and presence of flumazenil) in oocyte-expressed α1β3γ2L GABAA receptors using voltage clamp electrophysiology. The ability of diazepam to inhibit receptor labeling of purified α1β3γ2L GABAA receptors by 3[H]azietomidate was assessed in photoaffinity labeling protection studies. The impact of diazepam (in the absence and presence of flumazenil) on the anesthetic potencies of etomidate and ketamine was compared in a zebrafish model. Results At nanomolar concentrations, diazepam comparably potentiated etomidate-activated and GABA-activated GABAA receptor peak current amplitudes in a flumazenil-reversible manner. The half-maximal potentiating concentrations were 39 nM (95% CI, 27 to 55 nM) and 26 nM (95% CI, 16 to 41 nM), respectively. However, at micromolar concentrations, diazepam reduced etomidate-activated, but not GABA-activated, GABAA receptor peak current amplitudes in a concentration-dependent manner with a half-maximal inhibitory concentration of 9.6 µM (95% CI, 7.6 to 12 µM). Diazepam (12.5 to 50 µM) also right-shifted the etomidate-concentration response curve for direct activation without reducing the maximal response and inhibited receptor photoaffinity labeling by 3[H]azietomidate. When administered with flumazenil, 50 µM diazepam shifted the etomidate (but not the ketamine) concentration–response curve for anesthesia rightward, increasing the etomidate EC50 by 18-fold. Conclusions At micromolar concentrations and in the presence of flumazenil to inhibit allosteric modulation via the classical benzodiazepine binding site of the GABAA receptor, diazepam acts as an in vitro and in vivo competitive etomidate antagonist. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Prediction of the Anxiolytic Action Mediated by the GABA A Receptor by the Molecular Docking Method

The article considers the study in silico of the affinity of 3-[2-oxo-2-(4-phenyl-1-piperazinyl)ethyl]-4(3H)-quinazolinone (VMA-10-21 compound) to the benzodiazepine binding site of the GABA А receptor by molecular docking method. The computational experiment was carried out using a set of Autodock programs. As a result, the method for predicting the affinity of the simulated compounds to the benzodiazepine binding site of the GABA A receptor was developed. The highest correlation coefficient between the pKi value and the average docking energy in the benzodiazepine binding site (0.54) was obtained using a set of amino acids Tyr 58 and Tyr 159. The predicted Ki value of the VMA-10-21 compound is 2.864 nM, which suggests a high affinity of the studied compound to this receptor.

Synthesis and Biological Activity of Pyridopyridazine Derivatives: A Mini Review

This review presents most of the literature data about synthesis and biological activity of pyridopyridazine derivatives. There are six structural isomers of the bicyclic ring system containing pyridine moiety condensed with pyridazine nucleus. Pyridopyridazine derivatives show antitumor, antibacterial, analgesic and diuretics activities. The derivatives have been identified as the selective phosphodiesterase 5 and phosphodiesterase 4 inhibitors. Pyridopyridazines are novel class of GABA-A receptor benzodiazepine binding site ligands. Some of pyrido[3,2-c]pyridazine derivatives possess molluscicidal activity and can be used as biodegradable agrochemicals. The broad spectrum of biological activity of pyridopyridazine derivatives is the main reason for the preparation of new compounds containing this scaffold.