Charybdotoxin, potassium channel inhibition

Note. Barium block of K channels is very voltage dependent. Block by charybdotoxin and iberiotoxin is also voltage dependent. TEA+ block is voltage-dependent but not very steep. In all aforementioned cases the block increases with membrane hyperpolarization. The bold values indicate the relative selective concentration for the inhibitor of that type of potassium channel. K, = half-inhibition constant. For references, see text. 

Certain synthetic potassium channel openers have been shown to activate K a channels, such as NS-004 (Sargenteta/., 1993)andNS-1619. However, iberiotoxin was unable to reverse the functional effects of NS-004, and therefore its mechanism of action may also involve inhibition of calcium current rather than activation of K a channels. Some drugs (e.g., cro-makalim) that activate K -p channels have also been shown to activate K channels in aortic smooth muscle cells but not in other types of arterial smooth muscle. Since blockers of K a channels (charybdotoxin and <1 mM TEA+) had no effect on membrane potential hyperpolarizations or dilations to any of... 

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