The role of prostanoids in neonatal cerebral blood flow autoregulation.

The regulatory role of prostanoids in acute cerebrovascular adaptations in newborns was determined using awake neonatal piglets (ages 0-5 days, n = 60). Cerebral blood flow (CBF) was measured by radiolabelled microspheres before and 45 s after intracarotid injections of PGE1 (0.1-10 micrograms/kg, n = 6), PGE2 (0.01-2 micrograms/kg, n = 6), PGF2 alpha (0.01 microgram/kg, n = 8) and PGI2 (0.1 microgram/kg, n = 6). CBF increased with PGE1 (10 micrograms/kg) by 39.5% and with all doses of PGE2 (p < 0.01) compared to zero dose. PGF2 alpha, a known adult vasoconstrictor increased total CBF from 97 +/- 8 to 130 +/- 14 ml/min per kg. PGI2 also increased CBF by 27% (p < 0.01). When CBF and prostanoid levels were measured with balloon catheters placed at the aortic root and the descending aorta and were inflated to adjust arterial blood pressure (BP) from 17 to 117 mmHg, sagittal sinus concentrations of prostanoids inversely correlated with total CBF (for PGs, tau = -0.52 to -0.66, p < 0.001; for TXB2, tau = -0.91 to 0.99, p < 0.0001). During hypotension (MABP < 50 mmHg) PGE, PGF2(2)alpha, 6-keto-PGF1 alpha and TXB2 increased by 311 +/- 56, 330 +/- 50, 301 +/- 44 and 658 +/- 44%, respectively. Net cerebrovascular production [total CBF x (sagittal sinus-arterial plasma prostanoid concentration)] of PGE, PGF2 alpha, and 6-keto-PGF1 alpha and TXB2 increased during hypotension compared to normotension (BP = 50-90 mmHg). At MABP = 91-117 mmHg, net production of prostanoids increased by 142-31%.(ABSTRACT TRUNCATED AT 250 WORDS)