Abstract: AIM　To study the activation of choline on M₃-R in heart and observe the hemodynamic changes of rat and rabbit. METHODS　A cardiac catheter was inserted into the left ventricular cavity via the right carotid artery, then the HR, LVSP, LVEDP, and ±dp/dt were measured using a polygraph system. RESULTS　Choline was shown to decrease the hemodynamic assessments, such as HR, +dp/dt, LVSP and LVEDP. while the M₃-R antagonist 4-DAMP (4-diphenylacetoxy-N-methylpiperidine-methiodide) showed little effect on these assessments. It was found to reverse the hemodynamic effects of choline. CONCLUSION M₃ receptor agonist can produce negative inotropic and chronotropic effects on the heart of rat and rabbit.