Effects of dauricine on electrical and mechanical activities in the isolated guinea pig myocardium

The effects of dauricine(Dau) on electrical and mechanical activity were investigated in auricle and papillary muscle from guinea pigs. Dau 0.1 mM which reduced the force of contraction by 73.6% decreased the amplitude and dV/dtmax of action potential by 24.5% and 73.4%,respectively. Dau(1-300 microM) incaresed the duration of action potential(APD) to 20% and 90% repolarization and functional refractory period in a concentration-dependent way. But dV/dtmax of action potential and force of contraction were reduced almost equally by Dau also in a concentration-dependent manner. The effect that acetylcholine 30 microM shortened the APD of auricles was antagonized by Dau 30 microM. The effects of Dau can be explained by a non-specific inhibition of the current of Na+, Ca+ and K+.