Effect of xanthone from Kielmeyera coriacea stems on serotonergic neurons of the median raphe nucleus

Locomotor activity in the open-field test (OFT) was evaluated as a complementary measure. Xanthone (0.3 ng) or Way100635 (2.5 μg) reduced, whereas (+) 8-OH-DPAT (5.0 μg) increased immobility time in the FST. Way100635 (2.5 or 5.0 μg) completely reversed the effects of (+) 8-OHDPAT (5.0 μg), and potentiated the anti-immobility effect of the ineffective dose of xanthone (0.2 ng) in the FST. The association of effective doses of (+) 8-OH-DPAT (5.0 μg) and xanthone (0.3 ng) annulled the effect of each compound on immobility time. These results suggest that xanthone acts as an antagonist at 5-HT1A autoreceptors in MRN and increases serotonin (5-HT) availability in projection regions, proving to be a prototype drug that may be useful in mood isorders such as depression, or indeed be a beneficial adjunctive treatment improving the efficacy and/or accelerating the effects of antidepressant drugs in patients with major depression.