We examined the circulatory effects of SKF-82526-J, a new specific dopamine receptor agonist, using chronically instrumented neonatal lambs. Serial infusion of doses ranging from 1.4 to 337 micrograms/kg/min did not change cardiac output, heart rate, left atrial pressure, systemic arterial pressure (SAP) or vascular resistance (SVR). Pulmonary pressure (PAP) increased from 22.6 +/- 1.1 to 35.8 +/- 4.0 mm Hg at 337 micrograms/kg/min (p less than 0.005) and pulmonary resistance (PVR) changed from 0.099 +/- 0.01 to 0.15 +/- 0.03 mm Hg/ml/kg/min (p less than 0.025). After 3-12 min of recovery, SAP increased in all lambs (range 6-57 mm Hg), while PAP fell, without change in cardiac output. Thus, the ratio of PVR/SVR returned more quickly to baseline (4 min) than either PVR or SVR alone. We conclude, based on physiologic evidence, that the newborn lamb pulmonary circulation has no vasodilating dopamine receptors.