Staining of central neurons of the pteropod mollusk Clione limacina with fluorescein-labeled alpha-bungarotoxin

Fluorescein-labeled alpha-bungarotoxin (alphaBT/FITC) was used to identify neurons bearing acetylcholine receptors in the central nervous system of the pteropod mollusk Clione limacina. AlphaBT/FITC stained two small symmetrical neurons on the dorsal surface of the cerebral ganglia. The stain was highly specific and was completely blocked by preincubation with a very low concentration of unlabeled alpha-bungarotoxin (1 nM). Nicotinic receptor agonists and antagonists effectively blocked staining with alphaBT/FITC, while muscarinic agonists and antagonists had no effect. This provides evidence that alphaBT/FITC genuinely binds to acetylcholine receptors. The possible role of the alphaBT/FITC-stained cells in the hunting behavioral complex of Clione is discussed.