ALPHA-CONOTOXIN-IMPERIALIS-I INHIBITS NICOTINE-EVOKED HORMONE-RELEASEAND CELL-PROLIFERATION IN HUMAN NEUROENDOCRINE CARCINOMA-CELLS

alpha-Conotoxins are small peptides present in the venom of different species of marine snails of the Conus genus that target nicotinic acet ylcholine receptors (nAChRs), with a marked specificity for muscle-typ e nAChRs. alpha-Conotoxin Imperialis I (alpha-Ctx-ImI), from Conus imp erialis, has been recently described as a potent antagonist of mammali an neuronal alpha-bungarotoxin (alpha-Bgtx)-sensitive nAChRs. Human sm all cell lung carcinoma (SCLC) is a very aggressive tumor composed of neuroendocrine secretory cells. We demonstrated that human SCLC cells express neuronal-type alpha-Bgtx-sensitive nAChRs, and that their acti vation causes secretion of mitogenic hormones and stimulates cell prol iferation. alpha-Ctx ImI inhibits both these nicotinic effects, and co uld therefore be considered a new important tool for investigating hum an neuronal-type alpha-Bgtx-sensitive nAChRs.