| Research Abstract |
Pharmacological significance of drug induced vasodilatations in conductive and resistive coronary arteries were studied separately in unanesthetized and unrestrained dogs chronically implanted blood flow sensor and sonomicrometer elements in the circumflex branch of the left coronary artery, intra-vascular catheters into the aorta and vein and ECG electrodes in the pectral wall. Sublingual nitroglycerin 5 microgram/kg effectively increased left circumflex coronary diameter, the effect lasted 5-8 minutes. However, coronary blood flow, heart rate, blood pressure, left ventricular diameter, LVEDP and LVdp /dt were not significantly changed. With increasing dose up to 25 microgram/kg, these effects have not changed basically. By a rapid intravenous injection of the large doses, caused increases in cardiac output, LVdp /dt, heart rate, venous return and lowered the LVEDP. This indicates that nitroglycerin in clinical dose range acts solely to dilate large coronary i.e.,coronary conductive artery and does not dilate the coronary resistive artery. Most coronary vasodilators, such as dipyridamole, nifedipine, nicorandil, diltiazem, dilazep, produced a dilation in both conductive and resistive coronary arteries. From the above findings, nitroglycerin is a nobel characteristics to dilate selectively the conductive coronary artery which worthy to be named as the selective coronary conductive arterial dilator. This chracteristics give more beneficial effects angina pectoris.
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