Graded bioassay for demonstration of brain rescue from experimental acute ischemia in rats.

BACKGROUND AND PURPOSE This study explored the correlation between duration of focal ischemia and infarct volume in spontaneously hypertensive rats as a measure of outcome after neuroprotective intervention. METHODS We used 2,3,5-triphenyltetrazolium chloride staining to discriminate infarcted tissue and calculate infarct volume 24 hours after temporary tandem common carotid/middle cerebral artery occlusion lasting 5 to 150 minutes. We used a graded bioassay described by logistic function and executed by computer program (ALLFIT) to evaluate changes in infarct volume after increasing durations of ischemia. The method allowed us to calculate the maximal infarct volume (Volmax) and the duration of ischemia before reperfusion producing half-maximal infarct size (T50). Hypothermia and the N-methyl-D-aspartate antagonist CNS-1102 begun after the onset of ischemia were tested for their ability to reduce Volmax and prolong T50 as analyzed by ALLFIT. RESULTS Volmax was 180.6 +/- 22.4 mm3 and T50 was 45.9 +/- 5.8 minutes in control rats. Hypothermia (30 degrees C) applied during ischemia reduced Volmax by 66 mm3 and extended T50 by 50% (P < .05 for each comparison). CNS-1102, like hypothermia, extended T50 by 44% but did not have an effect on Volmax. CONCLUSIONS Analysis of the changes of infarct size after increasing durations of ischemia indicates that although both were protective, the two treatments tested may exhibit different profiles of efficacy. This method of analyzing ischemia-induced damage may be very sensitive for studying the efficacy and possible clinical use of neuronal protective therapies for hyperacute stroke.