Mechanisms mediating the coronary vascular response to behavioral stress in the dog.
Left circumflex coronary blood flow (CBF) was measured in eight mongrel dogs with 8 MHz continuous wave Doppler flow transducers during classical aversive conditioning. The cardiovascular condition response consisted of significant (P less than 0.01) increases in: (1) mean aortic pressure (16.1%), (2) d(left ventricular pressure)/dt (64.2%), and (3) heart rate (63.2%). The coronary vascular response to behavioral stress consisted of an initial late diastolic decrease in CBF (12.5%) between 5 and 10 seconds after conditional stimulus onset, followed by a significant increase in CBF (96.8%). Concurrently, late diastolic coronary vascular resistance (CVR) first significantly increased (21.9%), then significantly decreased (39.8%). The increase in CVR was attenuated by cardiac pacing and converted into a significant decrease after alpha-receptor blockade. The decrease in CVR was reduced either by cardiac pacing or cardioselective beta-receptor blockage and eliminated by the combination of alpha- and beta-receptor blockade. Thus, these data indicate that the coronary vascular response to stress consisted of two components: an initial alpha-adrenergic coronary vasoconstriction, followed by a more complex vasodilation which was probably mediated by metabolites released secondarily to increases in heart rate and inotropic state.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure; D002304:Cardiac Pacing, Artificial; D003214:Conditioning, Classical / Q000502:physiology; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000502:physiology; D004285:Dogs; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D013315:Stress, Psychological / Q000503:physiopathology*; D014655:Vascular Resistance
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D008790:Metoprolol