Figure 3.

Effects of K⁺ channel openers on K_ATP channels of rat skeletal muscle fibres in the absence of internal ATP. (a) Digital average of K_ATP current recorded in the excised inside-out macropatches, at −60 mV (V m), with high cytosolic KCl solutions on both sides of the membrane, in the absence (controls) (n=26 macropatches), or in the presence of the 2H-1,4-benzoxazine derivatives having the methyl (n=5 macropatches), ethyl (n=4 macropatches) or propyl (n=6 macropatches) groups at position 2 on the benzoxazine ring or in the presence of cromakalim (n=7 macropatches). C and O in the traces indicate closed and open channel levels, respectively. (b) Concentration–response relations of the 2H-1,4-benzoxazine derivatives having the –CH₃, –C₂H₅ or –C₃H₇ groups at position 2 of the benzoxazine ring, and of cromakalim on the K_ATP currents in the absence of ATP. All the compounds under investigation produced a concentration-dependent inhibition of the K_ATP current, (c) Log P plot versus the IC₅₀ of the 2H-1,4-benzoxazine derivatives and cromakalim. The calculated coefficient of correlation between the log P and IC₅₀ of the compounds under investigation was 0.8.