SB-616234 is a selective serotonin 5-HT<sub>1B</sub> receptor antagonist. In terms of affinity, it shows 50-fold selectivity for the serotonin 5-HT<sub>1B</sub> receptor over the serotonin 5-HT<sub>1D</sub> receptor and greater than 100-fold selectivity for the serotonin 5-HT<sub>1B</sub> receptor over other serotonin receptors. The drug is a silent antagonist of the serotonin 5-HT<sub>1B</sub> receptor. It dose-dependently increases serotonin levels in the dentate gyrus of the hippocampus in rodents via blockade of serotonin 5-HT<sub>1B</sub> autoreceptors. In addition, it augments the increased serotonin levels induced by the selective serotonin reuptake inhibitor (SSRI) paroxetine in this brain area in rodents. The drug produces antidepressant- and anxiolytic-like effects in rodents and anxiolytic-like effects in monkeys. It is orally active. SB-616234 was first described in the scientific literature by 2003.