The CBF Threshold and Dynamics for Focal Cerebral Infarction in Spontaneously Hypertensive Rats

Abstract

Two strategies were used to estimate the blood flow threshold for focal cerebral infarction in spontaneously hypertensive rats (SHRs) subjected to permanent middle cerebral artery and common carotid artery occlusion (MCA/CCAO). The first compared the volume of cortical infarction (24 h after ischemia onset) to the volumes of ischemic cortex (image analysis of [14C]iodoantipyrine CBF autoradiographs) perfused below CBF values <50 (VIC50) and <25 ml 100 g−1 min−1 (VIC25) at serial intervals during the first 3 h of ischemia. The infarct process becomes irreversible within 3 h in this model. In the second, measurements of CBF at the border separating normal from infarcted cortex at 24 h after ischemia onset were used as an index of the threshold. During the first 3 h of ischemia, VIC50 increased slightly to reach a maximum size at 3 h that closely matched the 24 h infarct volume. VIC25, in contrast, consistently underestimated the infarct volume by a factor of 2–3. CBF at the 24 h infarct border averaged 50 ml 100 g−1 min−1. Taken together, the results indicate that the CBF threshold for infarction in SHRs approaches 50 ml 100 g−1 min−1 when ischemia persists for ≥3 h. This threshold value is approximately three times higher than in primates. Since cortical neuronal density is also threefold greater in rats than in primates, the higher injury threshold in the rat may reflect a neuronal primacy in determining the brain's susceptibility to partial ischemia.

Correlation of early reduction in the apparent diffusion coefficient of water with blood flow reduction during middle cerebral artery occlusion in rats

“…In the 30-min group, the ADC 15 area corresponded best with the CBF 25 area. This CBF level is below the reported threshold for delayed infarction, [50 m1/100 g/min (20)] and is similar to that associated with acute energy failure (16), which supports the hypothesis that reduced ADC is associated with ATP depletion and consequent cellular edema. In the 90-min group, the ADC 15 area corresponded best with the CBF 30 -CBF 35 areas.…”

“…After 2 h of permanent ischemia, histological damage was associated with CBF levels of less than 24 m1/100 g/min (19). However, a much higher blood flow threshold of 50 ml/100 g/min during acute focal ischemia has been found to be associated with delayed (24-h) infarction (20). These findings suggest that the area with very early hyperintensity on D-MR images may be smaller than the area at risk for infarction.…”

“…The mean CBF 50 areas in the 30-and 90-min occlusion groups were very similar (73 ± 20% versus 74 ± 8%), but the CBF 15 , CBF 20 , CBF 25 , and CBF 30 areas were larger in the 90-min group (Table 2). Although none of the individual differences for each threshold were statistically significant, when examined collectively, the overall difference between the 30-and 90-min groups was statistically significant (P < 0.05).…”

“…CBF rates were estimated with a method that corrects for the "wash-out" volume of blood in the arterial and venous catheters (25). The percent of ischemic hemisphere with CBF rates less than 15,20,25,30,35,40, and 50 m1/100 g/min (CBF 15 , CBF 20 , CBF 25 , CBF 30 , CBF 35 , CBF 40 , and CBF 50 ) was determined for three sections from within the 2-mm thick slice of the MR images. Reported results are the mean of the three measurements.…”

Penumbra Detection using PWI/DWI Mismatch MRI in a Rat Stroke Model with and without Comorbidity: Comparison of Methods

“…A CBF threshold of 50 mL/100 g per minute (60% to 70% reduction from basal CBF) has been reported previously in the SHR strain, when ischemia persists for at least 3 hours (Jacewicz et al, 1992). This study highlights that rat strains may have different viability thresholds, particularly those strains which have underlying pathologies, such as the SHR and SHRSP.…”