Mechanism of action
In order to elucidate the mechanism by which V. cymosa extracts induce antinociceptive effect, animals were pre-treated with the non-selective opioid antagonist, naloxone. Figure 4 shows that naloxone (5 mg/kg) completely reverted the morphine (2.3 mg/kg) antinociceptive effect in tail flick model. Naloxone also reverted the antinociceptive activity of all V. cymosa extracts tested (at 30 mg/kg). Results of naloxone against V. cymosa extracts were comparable to those obtained with naloxone against morphine on the spinal model of analgesia.