Neosurugatoxin, a Specific Antagonist of Nicotinic Acetylcholine Receptors

Neosurugatoxin (NSTX) (3 nM-30 nM), recently isolated from the Japanese ivory mollusc (Babylonia japonica) exerted a potent antinicotinic action in the isolated guinea pig ileum. Specific 3H]nicotine binding to rat forebrain membranes was saturable, reversible, and of high affinity. Nicotinic cholinergic agonists exhibited a markedly greater affinity for 3H]nicotine binding sites than a muscarinic agonist, oxotremorine. Although alpha-bungarotoxin had no effect on 3H]nicotine binding, low concentrations (1 nM-1 microM) of NSTX inhibited 3H]nicotine binding in the forebrain membranes and its IC50 value was 69 +/- 6 nM. On the other hand, NSTX did not affect muscarinic receptor binding in the brain. These data indicate that NSTX may be of appreciable interest as a neurotoxin with a selective affinity for ganglionic nicotinic receptors.