CMPI hydrochloride is a potent positive allosteric modulator of α4β2 nAChRs (EC50 values are 20 and 18 nM for rat and human, respectively). Selective for hα4β2 over hα3β2, hα3β4 and hα7. Inhibits (α4)2(β2)3, muscle-type and Torpedo nAChRs (IC50 values are 0.5, 0.7 and 0.2 μM, respectively), but not (α4)3(β2)2 receptors. Exhibits ability to photoincorporate into aliphatic and nucleophilic amino acid side chains.