Alpha-conotoxin IMI is a 12-aa toxin isolated from the cone snail Conus imperialis venom. Alpha-conotoxin IMI is a potent blocker of the alpha/delta nicotinic acetylcholine channel receptors (nAChR) located on postsynaptic membranes. Alpha-conotoxin IMI inhibits in a voltage independent manner mammalian neuronal nAChRs (a3/b2 > a7 > a3/b4) and has no effect on nAChRs composed of a2/b2, a3/b2, a4/b2, a2/b4, a3/b4, or a4/b4 subunits. This toxin is highly active against the neuromuscular receptor in frog.H-Gly-Cys-Cys-Ser-Asp-Pro-Arg-Cys-Ala-Trp-Arg-Cys-NH2 (Cys2-Cys8, Cys3-Cys12) or H-GCCSDPRCAWRC-NH2 (Cys2-Cys8, Cys3-Cys12)