In Chinese medicine, it is said that Aconiti tuber has cardiotonic, diuretic and analgesic effects. Kim et al reported that alkaloid free part of Aconiti tuber, CHCl3 insoluble fraction, showed inotropic effect on isolated frog heart and inotropic effect is potenciated by n-butanol fractionation. To investigate the effect of Aconiti tuber butanol fraction on the mechanical and electrical properties of heart, change of active tension, excitability and refractory period of isolated rabbit atrium in the presence of butanol fraction were measured and the comparison with that of ouabain and quinidine was done. The observed results are as follows. 1. 5 X 10-4g/ml concentration of Aconiti tuber butanol fraction showed approximately same effect with therapeutic concentration of ouabain on the increment of contractile force, and the effect of 2 X 10-3g/ml was greater than that of 1 X 10-5g/ml of ouabain. 2. Acceleration of rate of contractile force increment in the presence of Aconiti tuber butanol fraction was greater than in ouabain, and the time to maximum tension was shorter in Aconiti tuber butanol fraction than in ouabain. 3. The excitability of isolated atrium was slightly increased at low concentration of Aconiti tuber butanol fraction, while decreased at higher concentration. 4. Aconiti tuber butanol fraction slightly prolonged refractory period of isolated right atrium at the concentration of 2 X 10-3g/ml.
