Scorpion venom inhibits carbamylcholine‐induced 86rubidium efflux from rat parotid acini

Abstract
The muscarinic agonist carbamylcholine stimulated 5‐fold 86Rb efflux from preloaded rat parotid acini. Apamin was without effect on this carbamylcholine‐induced 86Rb efflux. By contrast, the venom from Leiurus quinquestriatus (a scorpion from Israel) inhibited non‐competitively this efflux while being without effect on the carbamylcholine‐stimulated 45Ca efflux and amylase release. This heat‐resistant inhibitory effect of the venom was destroyed by boiling in the presence of dithiothreitol. These results suggest that the venom from L. quinquestriatus contains a toxin capable to block apamin‐insensitive calcium‐activated potassium channels in rat parotid acini.