SB-271046 also potently displaces [125I]-SB-258585 from rat and pig striatal and human caudate putamen membranes with pKis of 9.02, 8.55 and 8.81, respectively. SB-271046 competitively antagonizes 5-HT-induced stimulation of adenylyl cyclase activity with a pA2 of 8.71.  SB-271046 is found to be a competitive antagonist with a pA2 of 8.7 in the functional adenylyl cyclase assay which is in good agreement with its binding affinity. SB-271046 demonstrates no significant inhibitory activity at the major human P450 enzymes. 
SB-271046 produces an increase in seizure threshold over a wide-dose range in the rat maximal electroshock seizure threshold (MEST) test, with a minimum effective dose of 0.1 mg/kg p.o. and maximum effect at 4 hours post-dose. The level of anticonvulsant activity achieves correlated well with the blood concentrations of SB-271046 (EC50 of 0.16 μM) and brain concentrations of 0.01 μM–0.04 μM at Cmax.  SB-271046 is moderately brain penetrant (10%), subject to low blood clearance (7.7 mL/min/kg) with a good half-life in rats (4.8 hours), and has excellent oral bioavailability (>80%).  SB-271046 produces 3-fold and 2-fold increases in extracellular glutamate levels in both frontal cortex and dorsal hippocampus of rats, respectively, which may be used for the treatment of cognitive and memory dysfunction.  SB-271046 (20 mg/kg, orally gavage) 30 min prior to training Wistar rats, is found to reverse significantly the amnesia produced by administering scopolamine (0.8 mg/kg, i.p.) in the 6 hours post-training period. SB-271046 progressively and significantly decreases platform swim angle and escape latencies over the five sequential trials on four consecutive daily sessions compared to vehicle-treated controls in aged rats. SB-271046 also improves task recall as measured by significant increases in the searching of the target quadrant on post-training days 1 and 3.  SB-271046 (10 mg/kg, s.c.) produces a significant, tetrodotoxin-dependent, increase in extracellular levels of both glutamate and aspartate within the frontal cortex of rats, reaching maximum values of 375.4% and 215.3% of preinjection values, respectively. 
Radioligand binding is performed on membranes from HeLa cells stably transfected with the human 5-HT6 receptor and striatal tissue from adult rats, adult pigs and human caudate putamen tissues. Membranes are incubated with 1 nM [125I]-SB-258585 or 2 nM [3H]-LSD for 45 min at 37 ℃. Non-specific binding is defined by the inclusion of 10 μM methiothepin and the assay ias terminated by rapid filtration through Whatman GF/B filters.