In adults, dopexamine is a specific dopaminergic and Beta2-adrenergic agonist; its effects in neonates are unknown. Ultrasonic flow probes were placed around the ascending and descending aorta and cranial mesenteric artery of 0- to 2-day-old and 2-week-old piglets. Animals of each age group (9 to 14 per group) were subjected to (1) dopexamine infusion (5 microg/kg/min); (2) 30 minutes of hypoxia (inspired oxygen content 0.12) followed by 30 minutes of reoxygenation; and (3) dopexamine infusion during hypoxia and reoxygenation. In both age groups dopexamine alone increased ascending aorta blood flow (cardiac output minus coronary artery blood flow), mildly decreased mean arterial pressure, and increased cranial mesenteric artery blood flow. Compared to baseline values, 30 minutes of hypoxia produced significant (P <0.05, analysis of variance) decreases in cranial mesenteric artery blood flow in 0- to 2-day-old (58 +/- 13 ml/min vs. 30 +/- 8 ml/min) and 2-week-old (125 +/- 18 ml/min vs. 60 +/- 11 ml/min) piglets. In all cases blood flow returned to baseline values after reoxygenation. In both animal groups treated with dopexamine before hypoxia, the decreases in cranial mesenteric artery blood flow were eliminated (47 +/- 5 ml/min vs. 44 +/- 6 ml/min in 0- to 2-day-old piglets; 140 +/- 27 ml/min vs. 117 +/- 18 ml/min in 2-week-old piglets). Dopexamine may prove to be of clinical benefit when neonates are threatened by hypoxemia-induced decreases in intestinal blood flow.