Anxiolytic effects of N-(4,5-dihydro-5-oxo-1,2-dithiolo-[4,3,b]-pyrrole-6-yl)-N-methylformamide, a pyrroloformamide isolated from a marine Streptomyces sp., in adult zebrafish by the 5-HT system.

General anxiety disorders are among the most prevalent mental health problems worldwide. The emergence and development of anxiety disorders can be due to genetic (30-50%) or non-genetic (50-70%) factors. Despite medical progress, available pharmacotherapies are sometimes ineffective or can cause undesirable side effects. Thus, it becomes necessary to discover new safe and effective drugs against anxiety. This study evaluated the anxiolytic effect in adult zebrafish (Danio rerio) of a natural pyrroloformamide (PFD), N-(4,5-dihydro-5-oxo-1,2-dithiolo-[4,3,b]-pyrrole-6-yl)-N-methylformamide, isolated from a Streptomyces sp. bacterium strain recovered from the ascidian Eudistoma vannamei. The complete structure of PFD was determined by a detailed NMR analysis, including 1H-13C and 1H-15N-HBMC data. In addition, conformational and DFT computational studies also were performed. A group of fishes (n = 6) was treated orally with PFD (0.1, 0.5 and 1.0 mg/mL; 20 µL) and subjected to locomotor activity and light/dark tests, as well as, acute toxicity 96 h. The involvement of the GABAergic and serotonergic (5-HT) systems was investigated using flumazenil (a silent modulator of GABA receptor) and 5-HT1, 5-HT2A/2C and 5-HTR3A/3B receptors antagonists, known as pizotifen, granisetron and cyproheptadine, respectively. PFD was nontoxic, reduced locomotor activity and promoted the anxiolytic effect in zebrafish. Flumazenil did not inhibit the anxiolytic effect of the PFD via the GABAergic system. This effect was reduced by a pretreatment with pizotifen and granisetron, and was not reversed after treatment with cyproheptadine. Molecular docking and dynamics studies confirmed the interaction of PFD with the 5-HT receptor.Communicated by Ramaswamy H. Sarma.

Pyrroloformamide (PFD), isolated from the marine Streptomyces sp. associated ascidian Eudistoma vannamei, showed no toxicity in adult zebrafish but reduced its locomotor activity.The structural elucidation of PFD was determined by the analysis of 1D and 2D NMR and HRESIMS data.The density functional theory (DFT) study confirmed the existence of two conformers as determined by NMR spectra.The serotonergic system modulated the anxiolytic effect of PFD via the 5-HT receptor in adult zebrafish.Molecular docking and dynamics studies confirmed the interaction of PFD with the 5-HT receptor.

Anxiolytic-like effect of brominated compounds from the marine sponge Aplysina fulva on adult zebrafish (Danio rerio): Involvement of the GABAergic system.

Benzodiazepines are commonly used to treat disorders of the central nervous system, including anxiety. However, due to their adverse effects, there is a continuing interest in discovering new safe and effective drugs. Marine natural products have emerged as a prolific source of bioactive nitrogenated compounds. Aiming to discover new biologically active natural compounds, the marine sponge Aplysina fulva, a nitrogen-bearing heterocyst producer, was investigated. The main isolated compounds (4, 6, and 9) were evaluated on adult zebrafish (Danio rerio). A group of fishes (n = 6) was preliminarily subjected to acute toxicity, and open field tests using 0.1, 0.5, and 1.0 mg/mL (v. o.) of those compounds was performed. The anxiolytic effect was further investigated in the light/dark assay based on the locomotor response at zebrafish. Interactions through the GABAergic system were investigated using flumazenil, a silent modulator of GABA receptors. To improve the results, a study of molecular docking using the GABAA receptor also was performed. Based on the results, the bromotyrosine derivative compounds 4, 6, and 9 exhibited anxiolytic-like effects mediated by the GABAergic system.

Anxiolytic-like effect of chalcone N-{(4'-[(E)-3-(4-fluorophenyl)-1-(phenyl) prop-2-en-1-one]} acetamide on adult zebrafish (Danio rerio): Involvement of the GABAergic system.

Benzodiazepines are the standard drugs for the treatment of anxiety, but their undesirable side effects make it necessary to develop new anxiolytic drugs. The objective of this study was to evaluate the possible anxiolytic-simile effect of synthetic chalcone N-{(4'-[(E)-3-(4-fluorophenyl)-1-(phenyl) prop-2-en-1-one]} acetamide (PAAPFBA) on adult zebrafish (Danio rerio). PAAPFBA was synthesized with an 88.21% yield and its chemical structure was determined by 1H and 13C NMR. Initially, animals (n = 6/group) were treated (4 or 12 or 40 mg/kg, intraperitoneal) with PAAPFBA and were submitted to acute toxicity and open field tests. Then, other groups (n = 6/each) received PAAPFBA for the analysis of its effect on the Light & Dark Test. The participation of the GABAergic system was also assessed using the GABAA antagonist flumazenil. Molecular docking was performed using the GABAA receptor. The effect of PAAPFBA on anxiety induced by alcohol withdrawal was analyzed. PAAPFBA was non-toxic, reduced the locomotor activity, and showed an anxiolytic-like effect in both models. This effect was reduced by pre-treatment with the flumazenil. In agreement with in vivo studies, molecular docking indicated an interaction between chalcone and the GABAA receptor. The results suggest that PAAPFBA is an anxiolytic agent mediated via the GABAergic system.