The quantitative assessment of functional impairment and its correlation to infarct volume in rats with transient middle cerebral artery occlusion

The purpose of this study was to quantitatively assess motor activity and sensory functions and to determine their relationships to infarct severity by measuring infarct volume in rats with transient ischemic stroke. Male Sprague-Dawley rats (11 weeks old, n=42) were randomly divided into 4 separate groups; a sham operation group, and 1-h, 2-h and 3-h middle cerebral artery occlusion (MCAO) groups. Percent weights borne on paretic hind limbs were measured consecutively for 7 days starting from the day before the induction of ischemia. Fifty percent withdrawal threshold values of forepaws and hindpaws were measured using von-Frey hairs. Infarct volumes in the three ischemic groups, which were significantly different (p<0.01) from each other, were found to increase in size with ischemic time. The percent weight borne on paretic hind limb in the three MCAO groups were significantly lower than that in the sham group, and this functional deficit remained significant throughout the observational period (p<0.01). A significant correlation was found between infarct volumes and percent weight borne on paretic hind limbs after ischemia (-0.7<rho<-0.4, p<0.05). In contrast the 50% withdrawal threshold values of paretic forepaws and hindpaws in the three ischemic groups were not significantly different from those of the sham controls. Motor test findings, which were used to assess reductions in paretic hind limb weightbearing, were shown to be correlated with infarct volume. The present study shows that this test could be used as a tool to objectively and quantitatively assess functional outcome in MCAO rats.