Inhibition of evoked neurotransmitter release from rat hippocampus by a polypeptide toxin isolated from the marine snail Conus distans

The active fraction, isolated and partially purified from the crude venom of the marine snail Conus distans, with a molecular mass of about 25 kDa, inhibits neurotransmitter release in rat hippocampus. This toxin (distans Toxin) inhibits the electrically evoked tritium labelled noradrenaline release from rat hippocampal slices in a dose and time dependent manner. The neurotransmitter release is mainly regulated by N-type of voltage sensitive Ca 2+-channels. The distans toxin behaves as a partial antagonist of calcium in the buffer, possibly by competing with calcium for this type of voltage sensitive Ca 2+-channels.