Beagle puppy model of perinatal cerebral infarction

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Abstract
Perinatal cerebral infarction, or stroke, is a not uncommon finding in newborns who survive after intensive care. Asphyxia, with its component parts hypoxemia and hypotension, represents the most common cause of perinatal cerebral infarction and may result in neuropathological changes in the periventricular white matter. Previous studies have demonstrated regional alterations in cerebral blood flow (CBF) in response to hypoxemic insult. This work examines the effects of hypoxemia on regional cerebral prostaglandin levels in the developing brain, since some observers believe that local CBF is controlled in part by prostaglandins. In this study, newborn beagle pups were anesthetized, subjected to tracheotomy and artificially ventilated to maintain normoxemia and normocarbia. Mean arterial blood pressure (MABP) was continuously monitored by means of an indwelling catheter and transducer, and craniectomies were performed. When the pups were physiologically stabilized, they were randomly assigned to receive acute hypoxemic insult (pO2 14.0 +/- 1.55 mm Hg, mean +/- standard deviation) accomplished by altering the oxygen concentration in the inspired air) or to receive no insult (mean pO2 84.3 +/- 13.0 mm Hg). Fifteen minutes following stable hypoxemic or normoxic conditions, all pups underwent in vivo freezing of the intracranial contents under anesthesia followed by rapid sacrifice. No significant differences were noted between the MABP, pH, or pCO2 values for the control and hypoxemic pups during the experimental period. Regional cerebral prostaglandin data demonstrated a significant increase in prostaglandin (PG)E2 in the gray matter of hypoxemic pups when compared to the normoxic controls (p less than 0.02). No significant differences were noted for 6-keto-PGE1 alpha, the stable metabolite of prostacyclin, or thromboxane (TX)B2, the stable metabolite of TXA2, in the gray matter. In addition, although 6-keto-PGE1 alpha was significantly lower in the periventricular white matter of the hypoxemic pups (p less than 0.05), there were no changes in the white matter in either PGE2 or TXA2. This regional differential synthesis of PGE2 in response to hypoxemic insult may explain the relative failure of CBF to the periventricular white matter and thus the neuropathological alterations attributed to it.