DEVELOPMENTAL-CHANGES IN THE SENSITIVITY OF THE NEONATAL RAT-BRAIN TOHYPOXIC ISCHEMIC INJURY/

Developmental changes in the response of the neonatal rat brain to hyp oxic/ischemic injury were examined. Hypoxic/ischemic injury was produc ed by unilateral carotid ligation followed by exposure to hypoxia in 1 -(D1), 3-(D3), 5-(D5) and 7-day-old (D7) rats. Injury was produced in most D7 animals exposed to greater than or equal to 120 min of 7.6 or 8% oxygen after carotid ligation. The extent of neuronal injury was va riable, ranging from focal neuronal death to massive infarction. In D5 and D3 animals, there was a progressive decline in the extent of neur onal injury in response to hypoxia/ischemia. In the younger animals, b ilateral injury was occasionally seen. Sham-operated animals exposed t o hypoxia alone had numbers of karyorrhectic neurons similar to normal control animals in all age groups. The underlying developmental chang es which account for these differences are not yet known but are likel y to be multiple.