This is a family of potent toxins that function as ion-channel inhibitors for several different ions. Omega-Grammotoxin SIA is a VSCC antagonist that inhibits neuronal N- and P-type VSCC responses. Huwentoxin-IV, from the Chinese bird spider, is a highly potent neurotoxin that specifically inhibits the neuronal tetrodotoxin-sensitive voltage-gated sodium channel in rat dorsal root ganglion neurons. Hainantoxin-4, from the venom of spider Selenocosmia hainana, adopts an inhibitor cystine knot structural motif like huwentoin-IV, and is a potent antagonist that acts at site 1 on tetrodotoxin-sensitive (TTX-S) sodium channels. Study of the molecular nature of toxin-receptor interactions has helped elucidate the functioning of many ion-channels.