Cerebral Infarction Size According to the Duration of the Middle Cerebral Artery Occlusion in the Reversible and Irreversible Ischemic Infarction Models in the Rat

ABSTRACT

To establish a simple recirculation model in rats without craniectomy and to determine the recirculation time necessary to benefits the infarction area with restoration of the blood flow in a series of 30 adult rats, the authors induced irreversible ischemia(group I) in 15 rats through unilateral occlusion of the middle cerebral artery(MCA) by inserting a 16mm length of 4-0 nylon surgical thread through the internal carotid carotid artery(ICA). Reversible ischemia(group II) was induced by pullin the thread that occluded the MCA with hours recirculation in 5 rats. The author again divided the rats into 4 hours(Ia and Iia), 6 hours(Ib and Iib) and 12 hours(Ic and Iic) groups designated as according to the sacrifice time of rats in group I and the starting time of recirculation in group II following the MCA occlusion. The percentage of the infarction area to the total brain was calculated by a computer image analysis system, and the infarction size between reversible and irreversible groups were compared. The results showed that although the total average infarction sizes of irreversible ischemic groups were larger than those of reversible ischemic groups, the difference of the infarction size between each group o irreversible and reversible ischemia was not significant(group Ia Vs. Iia7.78+/-8.37% Vs. 3.28+/-1.98%; group Ib Vs. Iib 9.07+/-4.72% Vs. 6.61+/-3.19;group Ic Vs. Iic 8.35+/-4.47% Vs. 6.90+/-6.07%. p>0.05, one-way ANOVA test). However, the degree of difference of the infarction size between irreversible and reversible ischemia decrease along with the prolongation of ischemic duration(difference between group Ia and IIa4.5%;group Ib and Iib2.46%;group Ic and Iic.45%. The author concludes that ischemic brain injury may be decreased by making a restoration of the blood flow within 4 hours after occlusion of a blood vessel in rats, and this kind of reversible ischemic model may be useful in various studies on the focal cerebral ischemia without manipulation of the brain tissue and blood vessel.