We studied the effect of hypoxia on seven day old Sprague-Dawley rat pups and the structural changes in the preterm rat brain. The brain of the seven day old rat pup is comparable to that of 32 to 34 weeks premature newborn with the risk of developing periventricular hemorrhage and periventricular leukomalacia. Hypoxia with 8% O2 is known to produce brain damage.

MATERIALS - METHODS: Sprague-Dawley seven day old rat pups were placed in 500 ml airtight jars partially submerged in a 37° C water bath to maintain a constant thermal environment at 35° C ambient temperature with thermal couples. A humidified gas mixture of 8% O2 balance nitrogen combined was delivered into the jars via inlet and outlet portals at an approximate flow rate of 100 ml/min. The rat pups were exposed for 2.5 hours and allowed for 15 minutes in the open jars in the water bath. The pups were returned to their dames until 30 days of postnatal age at which time the animals were sacrificed. The gas mixture was calibrated commercially to precise concentration. Table

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Experimental pups were exposed to 7.94% O2 concentration. Randomly selected brains were analyzed for histological examination that were transected of 2 mm thickness intervals and stained with hematoxylin and eosin, Sevier-Munger, Luxol Fast Blue, GFAP, SNAP-25 (an antibody stain binding the“t” SNAR protein, localizing synapse rich areas). All stains were run in the study in one run on Ventana Medical System.

CONCLUSION - GFAP demonstrated increased gliosis of the paraventricular area at the anterior horn of the lateral ventricles at level 2. Failure to establish connections in these areas is one of the many reasons for the poor outcome in the preterm newborns with hypoxic injury.