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.