Serotonergic Neurons of Dorsal Raphe Nucleus on the Effect of a Xanthone from Kielmeyera coriacea Stems in Behavioral Tests

This study investigated the influence of serotonergic neurons of the dorsal raphe nucleus (DRN) on the effect of 1,3,7-trihydroxy-2-(3-methylbut-2-enyl)-xanthone, obtained from a hydroethanolic extract (HE) from Kielmeyera coriacea Mart. (Clusiaceae) stems. Intra-DRN microinjection (0.25 mu l/30 s) of xanthone or 5-HT1A ligands and its associations were performed in rats submitted to the forced swimming (FST) and to the open field (OFT) tests. Xanthone (0.3, 0.6 or 0.9 pmol), WAY(100635) (5-HT1A antagonist., 0.2, 0.4 or 0.8 nmol) or (+)pindolol (5-HT1A/1B/ssadrenergic antagonist: 0.2, 0.4 or 0.8 nmol) did not alter immobility time in the FST. The 5-HT1A agonist, (+)8-OH-DPAT (0.6 0.8, or 1.0 nmol) increases the immobility time in higher dose. Associated treatment Of WAY(100635) (0.8 nmol) or (-) pindolol (0.4 nmol) and xanthone (0.3 pmol), produced an anti-immobility effect, showing a synergic effect. Xanthone (0.3 pmol) abolished the increase on immobility time produced by (+)8-OH-DPAT (1.0 nmol). WAY100635 (0.8 nmol) blocked the increase in immobility time produced by (+)8-OH-DPAT (1.0 nmol). Crossings number in the OFT was not altered by any tested compound or associated treatment. These results suggest that the serotonergic neurons of the DRN, through the 5-HT1A somatodendritic autoreceptors, are involved in the xanthone effects on FST.