NITRIC-OXIDE DIRECTLY ACTIVATES CALCIUM-ACTIVATED POTASSIUM CHANNELS FROM RAT-BRAIN RECONSTITUTED INTO PLANAR LIPID BILAYER

Using the planar lipid bilayer technique, me tested whether NO directl y activates calcium-activated potassium (Maxi-K) channels isolated fro m rat brain, We used streptozotocin (STZ) as NO donor, and the NO rele ase was controlled with light, In the presence of 100-800 mu M STZ, th e Maxi-K channel activity increased up to 3-fold within several tens o f seconds after the light was on, and reversed to the control level se veral minutes after shutting off the light, Similar activation was obs erved with other NO donors such as S-nitroso-N-acetylpenicillamine and sodium nitroprusside, The degree of activity increase was dependent u pon the initial open probability (P-init) When the P-init was lower, t he activity increase was greater, These results demonstrate that NO ca n directly affect the Maxi-K channel activity, and suggest that the Ma xi-K channel might be one of the physiological targets of NO in brain. (C) 1997 Federation of European Biochemical Societies.