PMID: 6110777Apr 1, 1981Paper

Coronary blood flow and myocardial oxygen consumption after alpha adrenergic blockade during submaximal exercise

The Journal of Pharmacology and Experimental Therapeutics
P A Gwirtz, H L Stone

Abstract

The presence of a tonic coronary vasoconstriction mediated by the sympathetic nervous system has been demonstrated in conscious and anesthetized dogs during resting and hyperemic conditions. This vasoconstrictor tone could be eliminated by removing the left stellate ganglion and by alpha adrenergic blockade. This study examined the role of alpha receptors on coronary blood flow (CBF) in dogs during submaximal exercise. Eight does were chronically instrumented to measure CBF and left ventricular pressure. Six additional dogs were instrumented to record arterial blood pressure and measure myocardial oxygen consumption. Three weeks later, the dogs were submaximally exercised with or without phentolamine (1 mg/kg i.v.). At a workload of 6.4 km/hr, 16% treadmill elevation, heart rate (HR) increased from a resting level of 95 +/- 2 to 206 +/- 9 beats/min, CBF increased from 28 +/- 2 to 50 +/- 3 cm/sec and dP/dtmax increased from 3775 +/- 333 to 6811 +/- 859 mm Hg/sec. Alpha blockade increased resting HR to 136 +/- 16 beats/min (P less than .05). After alpha blockade, HR was 275 +/- 13 beats/min (P less than .01), CBF was 71 +/- 5 cm/sec (P less than .02) and dP/dtmax was 9419 +/- 856 mm Hg/sec (P less than .05) at a workload of 6.4 k...Continue Reading

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