BDS-II is a 43 amino acid peptidyl toxin isolated from the sea anemone Anemonia sulcat �venom. BDS-II was shown to be a specific Kv3.4 blocker. BDS-II blocked 70% of the Kv3.4 current in COS-transfected cells at a concentration of 2.8 mM. The blocking effect is rapid, direct and reversible. Recently it was shown that it blocks other Kv3 channels with similar potencies. BDS II inhibited the A type K+ current in human pulmonary artery smooth muscle cells. In skeletal muscle cell line (C2C12), BDS II inhibited single Kv channel currents and shifted the resting membrane potential in a dose dependent manner and in a similar way it inhibited Kv3.4 channels co-expressed with the KCNE3 auxiliary subunit in CHO cells. The inhibition of these channels was about ten times less potent than the inhibition of Kv3.4 channels expressed alone (IC50of about 1 mM and 10 mM respectively)�. Ion Channel Modulators> K+ Channel Blockers.