Failure of allopurinol to protect against cerebral injury when given after the start of hypoxia.

One cause of ischemic brain injury is free radical formation during recirculation. Allopurinol inhibits xanthine oxidase, an important source of free oxygen radicals. It is known that allopurinol pre-treatment has a protective action during cerebral ischemia. In the present study we exposed slices from the rat hippocampus to 9 minutes of hypoxia to test whether it is sufficient that allopurinol is present in the tissue at the time of reoxygenation. Forty-six slices loaded with allopurinol (10(-5) M) prior to reoxygenation (during hypoxia) were compared to 34 control slices. The response of the pyramidal cell population to orthodromic stimulation was reduced in both groups and there was not a significant difference between the two groups.