[The positive inotropic effect after washout of acetylcholine in isolated rabbit hearts]

To study the regular pattern and mechanism of positive inotropic effect after washout of ACh (rebound of myocardial contractile force) in isolated rabbit hearts.The changes of myocardial contractile force after perfusion and washout of ACh were observed in isolated Langendorff perfused rabbit hearts.Maximum rebound rate induced by ACh of 10(-8)-10(-3) mol/L were 2.20% +/- 1.70%, 6.71% +/- 3.40%, 9.18% +/- 3.54%, 14.16% +/- 3.27%, 4.37% +/- 5.86% and 1.03% +/- 6.86%, respectively. Compared with the ACh of 10(-5) mol/L in control group, adrenaline enhanced rebound of myocardial contractile force, maximum rebound rate in adrenaline group was 29.25% +/- 5.83% (P0.05), propranolol reduced rebound, and maximum rebound rate in propranolol group was 5.15% +/- 4.45% (P0.05), we had not detected rebound of myocardial contractile force in 800 s after addition ACh in verapamil group.In isolated rabbit heart, positive inotropic effect after washout of ACh has relevance to the activities of calcium current channel and beta-adrenergic receptor. Perhaps there are some different aspects in the mechanism of positive inotropic effect between perfusion of high concentration and after washout of ACh.