EFFECT OF ADENOSINE ON TOTAL AND REGIONAL CEREBRAL BLOOD-FLOW OF THE NEWBORN PIGLET

The effect of adenosine on total and regional CBF, measured by radiolabeled microspheres, was assessed in 16 anesthetized and ventilated newborn (1-3 days old) piglets. They received a ventriculocisternal perfusion containing either CSF alone (controls, n = 5) or CSF mixed with two different concentrations of adenosine (15 min each) randomly assigned using the following doses: 0.1 μM, 10 μM, 100 μM, 1mM (n = 4), or 10 mM (n = 6). Mean CSF adenosine concentration (by HPLC) before perfusion was 0.6 ± 0.4 μM. Total and regional CBF were not altered by the perfusion of CSF alone. All adenosine concentrations, except at low doses, increased total and regional CBF, without altering the cerebral metabolic rate for oxygen. Brainstem blood flow was increased by a mean of 110, 145, 306, and 378% with 10 μM, 100 μM, 1 mM, and 10 mM concentrations, respectively. Except for the highest concentration, CBF response was dose dependent in each region of the brain with the following order of potency: brainstem > periventricular area > telencephalon, midbrain, total brain, and cerebellum. These data indicate that, in the newborn, adenosine is a potent vasodilator of cerebral vessels. If the newborn brain can synthesize appropriate concentrations of adenosine, this nucleoside may play a major role in regional CBF regulation during the neonatal period.