ABSTRACT
<p><b>AIM</b>To study the regular pattern and mechanism of positive inotropic effect after washout of ACh (rebound of myocardial contractile force) in isolated rabbit hearts.</p><p><b>METHODS</b>The changes of myocardial contractile force after perfusion and washout of ACh were observed in isolated Langendorff perfused rabbit hearts.</p><p><b>RESULTS</b>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% (P < 0.05), propranolol reduced rebound, and maximum rebound rate in propranolol group was 5.15% +/- 4.45% (P < 0.05), we had not detected rebound of myocardial contractile force in 800 s after addition ACh in verapamil group.</p><p><b>CONCLUSION</b>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.</p>