Neosurugatoxin blocks nicotinic acetylcholine receptors in the brain

Neosurugatoxin, a neurotoxin isolated from the Japanese ivory mollusc (Babylonia japonica ) is a nicotinic antagonist with a specificity towards ganglionic nicotinic receptors. At low concentration (5 x 10(?8) M) neosurugatoxin inhibited the release of [(3)H]dopamine evoked by 1,1-dimethyl-4-phenylpiperazinium (DMPP) from rat striatal nerve terminals, without affecting the response to K(+)-depolarisation. In contrast, ?bungarotoxin did not antagonise the action of DMPP. Neosurugatoxin also inhibited [(3)H] nicotine binding to rat brain membranes but had no effect on [(125)I]?bungarotoxin binding to the same tissue preparation. These results support the view that functional nicotinic receptors in the CNS resemble ganglionic nicotinic receptors. Neosurugatoxin has considerable potential as a useful probe for such receptors in the brain.