Coronary dilation with carotid chemoreceptor stimulation in cardiac-denervated dogs.

The coronary vasodilation that is secondary to carotid chemoreceptor stimulation (CCS) was compared in normal (N) and in cardiac-denervated (CD) conscious dogs. Under base-line conditions, CD only differed from N dogs by greater (P less than 0.01) increases in mean arterial pressure (MAP) with CCS. Coronary blood flow (CBF) increased similarly in N (146 +/- 18%) and CD (126 +/- 15%) dogs, and coronary resistance (CR) fell to a similar extent in N (53 +/- 3%) and CD (43 +/- 5%) dogs. After muscarinic and beta-adrenergic blockade, CCS resulted in similar increases in MAP in N and CD dogs; increases in CBF averaged 122 +/- 15 and 115 +/- 12% in N and CD dogs, respectively. Decreases in CR with CCS averaged 46 +/- 3 and 40 +/- 5% in N and CD dogs, respectively. alpha 1-Adrenergic blockade prevented the increases in MAP with CCS and resulted in smaller (P less than 0.01) increases in CBF, similar in N (77 +/- 13%) and in CD (69 +/- 10%) dogs. CR fell to the same extent in N (40 +/- 4%) and CD (37 +/- 5%) dogs. Additional blockade of alpha 2-adrenergic receptors further limited the increases in CBF with CCS in N (20 +/- 5%) and CD (28 +/- 7%) dogs; decreases in CR were attenuated similarly in N (13 +/- 5%) and CD (21 +/- 5%) dogs. Thus, in conscious dogs, cardiac nerves contribute little to the coronary dilation after carotid chemoreceptor stimulation.