Highly potent and selective competitive antagonist for α3β2 subunit-containing nicotinic receptors (IC50 = 0.5 - 3.5 nM at α3β2 expressed in Xenopus oocytes). Also potently blocks β3-containing neuronal nicotinic receptors. Displays > 200-fold selectivity for α3β2 over α2β2, α4β2 and α3β4.