Psi-conotoxins act on postsynaptic membranes, and act as non-competitive antagonist of nicotinic acetylcholine receptors (nAChR). Reversibly inhibits both adult- and fetal-types nAChR. The inhibition potency against the adult- (alpha-1/beta-1/epsilon/delta) is higher than against the fetal-type (alpha-1/beta-1/gamma/delta). Induces flaccid paralysis in goldfish, but does not induce any remarkable behavior in mice and does not block action potential in directly stimulated frog muscle preparations. Expressed by the venom duct. The cysteine framework is III (CC-C-C-CC). Classified in the M-4 branch, since 4 residues stand between the fourth and the fifth cysteine residues. Does not show inhibitory effects against the mouse muscle subtype sodium channel Nav1.4/SCN4A. Belongs to the conotoxin M superfamily.