Abstract. The exact time profile of
superoxide generation during
anoxia-reoxygenation and
ischemia-reperfusion was assessed in the feline cerebral cortex in vivo using a chemiluminescence technique with a probe specific for
superoxide, 2-methyl-6-[p-methoxyphenyl]-3,7-dihydroimidazo[1,2-alpha]pyrazin-3-one (
MCLA).
MCLA solution was superfused on the cortex throughout the protocol, and
MCLA chemiluminescence was measured using a newly developed photon counting system. Reflectance at 398 nm was simultaneously measured to compensate for hemodynamic artifacts resulting from cerebral blood volume changes. In 19 animals, a 90-second
anoxia was induced by the inhalation of 100%
nitrogen followed by a 40-minute reoxygenation. The chemiluminescence decreased during the period of
anoxia (p < 0.01) and then exceeded the baseline level at 15 and 20 minutes after reoxygenation (p < 0.05). In six animals,
superoxide dismutase (SOD) was continuously superfused and
anoxia-reoxygenation was performed in the same manner. The chemiluminescence decreased during the period of
anoxia (p < 0.05) but did not exceed the baseline level during the reoxygenation period, indicating that an increase in
superoxide production was the main cause of the chemiluminescence increase. In eight animals, a 15-minute forebrain
ischemia was induced by the occlusion of the bilateral common carotid arteries with systemic
hypotension (systolic blood pressure less than 50 mmHg) followed by a 30-minute reperfusion. The chemiluminescence decreased during the period of
ischemia (p < 0.01) and then increased at 20 and 25 minutes after reperfusion (p < 0.05). These results indicate that
superoxide generation decreases during
anoxia and
ischemia and then increases within 20 minutes after reoxygenation or reperfusion.