Calcium channel antagonists: ω-conotoxin defines a new high affinity site

The ω-conotoxins, a class of Ca2+ channel antagonists from fish-hunting marine snails, have recently been described (Olivera, B. M., McIntosh, J. M., Zeikus, R., Gray, W. R., Varga, J., Rivier, J., de Santos, V., and Cruz, L. J. (1985) Science, 230, 1338-1343). One of these peptide neurotoxins, ω-conotoxin GVIA, was radiolabeled with iodine, and the 125I-labeled toxin was shown to bind specifically to high affinity sites on chick brain synaptosomes.