Adenosine Mediates Decreased Cerebral Metabolic Rate and Increased Cerebral Blood Flow During Acute Moderate Hypoxia in the Near‐Term Fetal Sheep

摘要: Exposure of the fetal sheep to moderate severe hypoxic stress results in both increased cortical blood flow and decreased metabolic rate. Using intravenous infusion 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a selective adenosine A1 receptor antagonist that is permeable brain barrier, we examine role receptors mediating responses hypoxia. The effects DPCPX blockade are compared controls as well animals receiving 8-(p-sulfophenyl)-theophylline) (8-SPT), non-selective which has been found be barrier impermeable. Laser Doppler probes, tissue PO2, thermocouples were implanted cerebral cortices near-term sheep. Catheters placed brachial artery sagittal sinus vein for collection samples gas analysis. Three seven days later 30-min period hypoxemia (arterial PO2 10–12 mmHg) studied with administration 8-SPT, DPCPX, or vehicle. Cerebral rate was determined by calculation heat production oxygen consumption. In response hypoxia, control experiments demonstrated 42 ± 7 % decrease 35 10 reduction contrast, during hypoxia resulted no significant change consumption, suggesting involved lowering not altered 8-SPT infusion, mediated located outside barrier. increase flow. did this flow, however attenuated increases indicating but via receptor. summary, appears play key defences, acting O2 delivery A2 inside These data show first time mammalian fetus an important mediator