SB-271046 is a selective and orally active 5-HT6 receptor antagonist. 5-HT6 belongs to GPCR which stimulates adenylate cyclase via Gs, which cloned from rat striatum. SB-271046 substituted [125I]-SB-258585 and [3H]-LSD from human 5-HT6 receptors which recombinantly expressed in HeLa cells in vitro (pKi 8.92 and 9.09 respectively). SB-271046 also transfered [125I]-SB-258585 from human caudate putamen and rat and pig striatum membranes (pKi 8.81, 9.02 and 8.55 respectively). By 5-HT alone or after increasing concentrations of SB-271046 (10, 30, 100 and 300 nM) stimulates adenylyl cyclase activity in HeLa cells stably expressing human 5-HT6 receptors. The affinities of SB-271046 in human (pKi 8.81), pig (pKi 8.55) and rat (pKi 9.02) were similar suggesting a lack of species differences in 5-HT6 receptor for this given ligand. SB-271046 has greater than 200 fold selectivity over 69 other receptor, enzyme and binding sites, containing all other 5-HT receptor subtypes tested. SB-271046 did not alter basal levels of 5-HT, DA and NA in either brain region. In contrast, administration of SB-271046 (10mg.kg-1s.c.) produced an important and tetrodotoxin-dependent acceleration in extracellular levels of both glutamate and aspartate within the frontal cortex, reaching maximum values of 375.482.3 and 215.362.1% of preinjection values, respectively.