High-conductance calcium-activated potassium channels: validated targets for smooth muscle relaxants?

High-conductance, calcium-activated potassium (Maxi-K) channels represent a group of proteins with diverse physiologic functions. Although the role of Maxi-K channels in the CNS is complex and still an area of active academic research, there appears to be better agreement concerning the contribution of these channels to the regulation of smooth muscle tone and, thus the expectations remain high for Maxi-K channel openers having use in the treatment of hypertension, overactive bladder, asthma or erectile dysfunction. Despite this consensus view, at the present time, there is only one compound that targets Maxi-K channels in clinical development for overactive bladder conditions. In the present review, the latest developments in the identification of potent and selective Maxi-K channel openers and their utility in the treatment of smooth muscle disorders will be discussed.