Constriction of the epicardial coronary artery induced by alpha-adrenergic stimulation

Effects of alpha adrenergic stimulation on diameter change of the epicardial coronary artery were studied in in-situ canine heart. The diameter of the left circumflex coronary artery (LCX) was continuously measured by 10 MHz PZT crystals applied to the external wall of the LCX. Aortic pressure was measured using high fidelity catheter-tip manometer. Enhanced activity of alpha adrenergic receptor by humoral and/or somatic nerve stimulations caused a reduction of the LCX diameter despite of the systemic pressure rise.