Anxiolytic-like effect of natural product 2-hydroxy-3,4,6-trimethoxyacetophenone isolated from Croton anisodontus in adult zebrafish via serotonergic neuromodulation involvement of the 5-HT system

Benzodiazepines are highly effective in combating anxiety; however, they have considerable adverse effects, so it is important to discover new safe anxiolytic agents. This study was designed to investigate the effect of the natural product 2-hydroxy-3,4,6-trimethoxyacetophenone (HTMCX) on anxiety and seizure behavior in adult zebrafish and its possible mechanisms of action. The acute toxicity of 96 h of HTMCX was analyzed, and the open and light/dark field tests (n = 6 animals/group) were used to assess the anxiety behavior of animals treated with HTMCX. In addition, the mechanisms of action were investigated with antagonists of the GABA_A, 5-HT receptors, and molecular anchorage study. Pentylenetetrazole (PTZ) was used to induce seizure by immersion. As a result, acetophenone HTMCX (1, 3 and 10 mg/kg; v.o.) was non-toxic and affected locomotor activity. The higher doses (3 and 10 mg/kg; v.o.) produced signs of anxiolytic action in the light/dark test, and this effect was reversed by the pizotifen (antagonist 5HTR₁ and 5HTR_2A/2C), having the potential to form a complex with 5HTR1B. However, the anxiolytic effect of HTMCX has not been abolished by flumazenil (antagonist GABA_A), cyproheptadine (antagonist 5HTR_2A), and granisetron (antagonist 5HTR_3A/3B). Therefore, HTMCX demonstrated an anxiolytic effect, suggesting that the 5HTR₁ and 5HTR_2C receptors may be involved in the pharmacological performance of this acetophenone in the central nervous system.