Oleanolic acid promotes orofacial antinociception in adult zebrafish (Danio rerio) through TRPV1 receptors.

This study aimed to evaluate the antinociceptive effect of oleanolic acid using adult zebrafish models of orofacial pain. Acute nociception was induced by formalin, capsaicin, cinnamaldehyde, menthol, acidified saline or glutamate (cutaneous modes) and hypertonic saline (corneal model). In another set of experiments, animals were pre-treated with naloxone, L-NAME, methylene blue, ketamine, camphor, HC-030031, mefenamic acid, ruthenium red or amiloride to investigate the mechanism of antinociception. The involvement of central afferent C-fibers was also investigated. A molecular docking was performed using the TRPV1 channel. Motor activity was evaluated with the open field test. Pre-treatment with oleanolic acid significantly reduced nociceptive behavior associated with acute pain. Antinociception was effectively inhibited by ruthenium red and capsaicin-induced desensitization. Presence of trpv1 was confirmed by RT-PCR in cerebral tissue of zebrafish. In line with in vivo experiments, docking studies indicated that oleanolic acid may interact with TRPV1. Results confirm the potential pharmacological relevance of oleanolic acid as an inhibitor of orofacial nociception mediated by TRPV1.