Effects of Acetyicholine on Large and Small Coronary Arteries in Conscious Dogs1

The effects of acetylcholine, 1 0 pg/kg i.v., were examined in nine conscious dogs on measurements of left ventricular pressure, dP/dt, aortic pressure, heart rate, coronary blood flow, left circumflex external coronary arterial diameter, arterial and coro-nary sinus 02 content and calculations of late diastolic coronary resistance and left circumflex internal coronary cross-sectional area. In conscious dogs in the absence of autonomic blockade, acetylcholine induced a rapid, transient response characterized by hypotension and peak increases in coronary blood flow (+135 ± 1 4%) and coronary sinus 02 content (+5.0 ± 0.5 volume percent) and decreases in late diastolic coronary resistance (-65 ± 3%). The peak large coronary arterial effects were observed 60 sec later at a time when arterial pressure, left ventricular end-diastolic pressure, left ventricular dP/dt and heart rate were no