NEGATIVE INOTROPIC ACTION OF CORYNANTHINE IN THE GUINEA-PIG PAPILLARY-MUSCLE IS ATTENUATED BY GLIBENCLAMIDE

1. The change in force and rate of rise of force contraction in the gu inea pig papillary muscle were measured. 2. Corynanthine, an alpha-1 a drenoceptor blocking agent, produced direct negative inotropic action and inhibited the isoprenaline positive inotropic action ih a dose-dep endent manner (3, 10 and 30 mu mol/l). 3. Addition of 1 mu mol/l glibe nclamide, a potent inhibitor of ATP-sensitive potassium channels, sign ificantly antagonized the direct negative inotropic action of corynant hine, but had no effect on the antagonism between isoprenaline and cor ynanthine. 4. The relationships between isoprenaline and corynanthine, and corynanthine and glibenclamide are discussed.