Animal experiment:

Seven days post surgery animals are placed in microdialysis cages for overnight habituation prior to microdialysis experimentation. The following morning microdialysis probes (2 mm cuprophane membrane) are implanted, via the guide cannulae, into the frontal cortex and/or dentate gyrus. Probes are perfused with artificial cerebrospinal fluid (aCSF) containing NaCl 145 mM, KCl 2.7 mM, MgCl2 1.0 mM, CaCl2 1.2 mM, Na2HPO4 2.0 mM (pH 7.4) at a flow rate of 1 μL/min. A 30 min sampling regime is used throughout the microdialysis procedure. Following a 2 h equilibration period, 3 microdialysis samples are collected to establish basal extracellular levels of 5-HT. Guinea pigs are then dosed with vehicle (1% methyl cellulose, 1 mg/kg p.o.), paroxetine (3 mg/kg p.o.) or SB-616234A (3, 10 or 30 mg/kg p.o.). Microdialysis samples are collected for a further 5 h following drug administration. 5-HT content of microdialysate samples is measured using high performance liquid chromatography (HPLC) with electrochemical detection (ECD). At the end of the experiment probes are removed and animals return to their home cage. Animals are re-used in a randomised cross-over design with 7 days between uses and a maximum of 4 uses per subject.

SB-616234A is a selective and orally bioavailable 5-HT1B receptor antagonist, with anxiolytic and antidepressant activity.

SB-616234A possesses high affinity for human 5-HT1B receptors stably expressed in Chinese hamster ovary (CHO) cells (pKi 8.3 ± 0.2), and is over 100-fold selective for a range of molecular targets except h5-HT1D receptors (pKi 6.6 ± 0.1). Similarly, affinity (pKi) for rat and guinea pig striatal 5-HT1B receptors is 9.2 ± 0.1. In [35S]-GTPγS binding studies in the human recombinant cell line, SB-616234A acts as a high affinity antagonist with a pA2 value of 8.6 ± 0.2 whilst providing no evidence of agonist activity in this system. In [35S]-GTPγS binding studies in rat striatal membranes, SB-616234A acts as a high affinity antagonist with an apparent pKB of 8.4 ± 0.5, again whilst providing no evidence of agonist activity in this system. SB-616234A (1 μM) potentiates electrically stimulated [3H]-5-HT release from guinea pig and rat cortical slices (S2/S1 ratios of 1.8 and 1.6, respectively)[2].

SB-616234A reverses the 5-HT1/7 receptor agonist, SKF-99101H-induced hypothermia in guinea pigs in a dose related manner with an ED50 of 2.4 mg/kg p.o. SB-616234A produces dose-related anxiolytic effects in both rat and guinea pig maternal separation-induced vocalisation models with an ED50 of 1.0 and 3.3 mg/kg i.p., respectively[1]. SB-616234A (0.3-30 mg/kg p.o.) causes a dose-dependent inhibition of ex vivo [3H]-GR125743 binding to rat striatal 5-HT1B receptors with an ED50 of 2.83 ± 0.39 mg/kg p.o[1].

[1]. Lee A.Dawson, et al. Characterisation of the selective 5-HT1B receptor antagonist SB-616234-A (1-[6-(cis-3,5-dimethylpiperazin-1-yl)-2,3-dihydro-5-methoxyindol-1-yl]-1-[2′-methyl-4′-(5-methyl-1,2,4-oxadiazol-3-yl)biphenyl-4-yl]methanone hydrochloride): In vivo neurochemical and behavioural evidence of anxiolytic/antidepressant activity. Neuropharmacology Volume 50, Issue 8, June 2006, Pages 975-983 [2]. Scott C, et al. SB-616234-A (1-[6-(cis-3,5-dimethylpiperazin-1-yl)-2,3-dihydro-5-methoxyindol-1-yl]-1-[2'methyl-4'-(5-methyl-1,2,3-oxadiazol-3-yl)biphenyl-4-yl]methanone hydrochloride): a novel, potent and selective 5-HT1B receptor antagonist. Neuropharmacology. 2006 Jun;50(8):984-90. Epub 2006 Mar 20.