Influence of the autonomic nervous system on coronary blood flow during partial stenosis.

Partial coronary stenosis produces cyclical changes in coronary blood flow (CBF) which are the result of spontaneous aggregation and disaggregation of platelet plugs at the site of occlusion. The possible influence of the autonomic nervous system on this phenomenon has not been hitherto determined. The present study was performed in 20 chloralose-anesthetized dogs in which the effects of bilateral vagotomy and stellectomy were examined during partial stenosis of the left circumflex coronary artery. Vagotomy reduced the frequency of CBF oscillations from 11.5 +/- 2.1 to 5.0 +/- 2.1 cycles/hr (p less than 0.05). The magnitude of the flow changes was reduced from 13.8 +/- 4.0 to 9.7 +/- 3.0 ml/min (NS). Bilateral cervical stellectomy reduced the frequency of CBF changes from 7.8 +/- 2.7 to 3.7 +/- 1.3 cycles/hr (p less than 0.025) and their magnitude from 10.6 +/- 2.5 to 5.6 +/- 1.8 ml/min (P less than 0.05). In five dogs in which cyclical CBF changes were reduced or abolished by decentralizing the stellate ganglia, electrical stimulation of the main body of the left ganglion evoked or enhanced the oscillations in two dogs, had no distinct effect in two dogs, and elicited no response in one dog. A 5-minute infusion of 0.5 microgram/kg/min and 0.75 microgram/kg/min epinephrine (four dogs) provoked the CBF changes in all animals for a period of 5 to 10 minutes. Blockade of muscarinic receptors by 0.2 mg/kg atropine resulted in a significant attenuation of flow changes, which may at least in part have been due to a direct effect of atropine on platelets. We conclude that cardiac sympathetic tone significantly influences the CBF pattern during critical coronary stenosis. While the afferent limb of the vagus may in part mediate this effect via a reflex increase of adrenal medullary catecholamines, the role of the efferent vagus awaits further clarification.