A NEW MODEL OF TRANSIENT CEREBRAL-ISCHEMIA IN NEONATAL RATS

A new model of transient cerebral ischemia in 10-day-old rats is descr ibed. Under microscopic guidance, the right external and internal caro tid arteries were electrically coagulated. A solid 0.47 mm diameter ny lon thread was inserted into the right common carotid artery toward th e ascending aorta up to 10-12 mm from the upper edge of the sternomast oid muscle (preischemic rats). A 60-min cerebral ischemia was induced by clamping the left external and internal carotid arteries (ischemic rats), followed by 3-h recirculation. P-31 magnetic resonance (MRS) sp ectroscopic studies revealed that severe intracellular acidosis occurr ed and ATP disappeared completely for at least the last 20 min of isch emia. Cerebral blood flow (CBF), measured by the hydrogen clearance te chnique, decreased to similar to 11% of the preischemic level in the f rontal cortex soon after the induction of ischemia. On resuscitation, ATP recovered completely and the preischemic intracellular pH level wa s restored within 180 min. CBF had recovered to similar to 30% of the preischemic level at 5 min after resuscitation. The CBF recovery was n ot complete even at 180 min after resuscitation. With this model, the effects of pure ischemia without hypoxia on the neonatal brain and the process of recovery from transient ischemia can be studied.