PGE2 does not act at carotid sinus to raise arterial pressure in conscious sheep

Conscious chronically instrumented adult female sheep were used to determine whether direct action of prostaglandin E2 (PGE2) on the carotid sinus baroreceptors contributes to the pressor response observed during infusion of PGE2 into the common carotid artery (CCA). During infusion of PGE2 into the CCA caudal to an intact carotid sinus, into the CCA caudal to a denervated carotid sinus, and into the external carotid artery, mean arterial pressure (MAP) rose 17, 22, and 17 mmHg, respectively (P less than 0.01). Heart rate (HR) rose 6, 6, and 8 beats/min, respectively (P less than 0.05). Cardiac output (CO) was also measured by indicator dilution using indocyanine green. In these experiments with infusion of PGE2 into the external carotid artery, MAP rose 15 mmHg (P less than 0.01), HR increased 6 beats/min (P less than 0.05), CO did not change, and total peripheral resistance (TPR) increased 23% (P less than 0.01). With infusion of PGE2 past a denervated carotid sinus, MAP rose 20 mmHg (P less than 0.01), HR rose 4 beats/min (P less than 0.05), CO did not change, and TPR increased 29% (P less than 0.01). There were no statistically significant differences in MAP or HR responses when PGE2 was infused past an intact carotid sinus, past a denervated carotid sinus, or beyond the carotid sinus. There is no evidence that direct action of PGE2 on carotid sinus baroreceptors either augments or inhibits the observed pressor effect of intracarotid PGE2. Intracarotid PGE2 acts rostral to the carotid sinus to increase MAP, HR, and TPR in conscious sheep.