Neosurugatoxin blocks an alpha-bungarotoxin-sensitive neuronal nicotinic acetylcholine receptor

Neosurugatoxin (NSTX), a neurotoxin isolated from the Japanese ivory mollusc Babylonia japonica, is a potent neuronal nicotinic acetylcholine receptor (nAChR) antagonist. Hitherto, NSTX has been found to block only neuronal nAChRs that are insensitive to alpha-Bgt. Here, we report for the first time that NSTX blocks an alpha-Bgt-sensitive nAChR on an identified insect motor neurone. Bath-applied NSTX at a concentration of 10 nM and above reversibly blocks the nicotine-induced depolarizations recorded from the cockroach (Periplaneta americana) fast coxal depressor motor neurone (Df) and is without effect on GABA-induced responses detected on the same cell. NSTX is among the most potent blockers tested to date on nAChRs of motor neurone Df.