Yangonin, a kavalactone from kava, reduced pain sensitivity and inflammation-induced pain in rats when injected into the spinal cord. These effects were blocked by a cannabinoid 1 (CB1) receptor antagonist, indicating yangonin acts through CB1 receptors. Yangonin did not affect nerve injury-induced pain. Kavain, another kavalactone, had no effect on any pain type tested.
Chronic MDMA use damages serotonin transporters (SERT) in the brain, which is linked to addiction and impaired decision-making. In rats, the cough suppressant dextromethorphan (DM) partially reversed this damage: co-administration with MDMA restored SERT binding by about 23% after 14 days compared to MDMA alone. Behavioral tests showed that MDMA-induced reward and hyperactivity were associated with lower SERT activity, and DM helped restore both SERT levels and serotonin fiber density. The findings suggest DM may protect against MDMA's neurotoxic effects on the brain's reward and motivation circuits.