NBUMP is a highly selective 5-HT<sub>1A</sub> receptor partial agonist (K<sub>i</sub> = 0.1 nM; IA = 40%) with an arylpiperazine structure. It is one of the highest affinity ligands for the 5-HT<sub>1A</sub> receptor known. It displays 460- and 260-fold selectivity for 5-HT<sub>1A</sub> over the ñ<sub>1</sub>-adrenergic and D<sub>2</sub> receptors, respectively.