Highly Reproducible Rat Model of Reversible Forebrain Ischemia – Modified Four-Vessel Occlusion Model and its Metabolic Feature

Summary.

 Background: The four-vessel occlusion method introduced by Pulsinelli et al. is widely used as an experimental model for reversible forebrain ischemia in rats.

 Method: In this study, we further developed highly reproducible model of reversible forebrain ischemia. Under the microscope the visible vertebral arteries at the second vertebra could be easily electrocauterized and completely cut to yield complete cessation of circulation of both vertebral arteries. After 24 hours, male Wistar rats were subjected to 15, 30 and 45 minutes of forebrain ischemia by occluding both common carotid arteries with Sugita's temporary clips. ³¹P-magnetic resonance spectra (³¹P-MRS) and ¹H-magnetic resonance images (¹H-MRI) were obtained with a 6.3-T spectrometer to investigate sequential change of the in vivo brain metabolism. Electroencephalogram and the cortical blood flow by laser Doppler flowmetry were measured during ischemia and recirculation. Determination of endogenous superoxide scavenging activity in the brain cortex was performed by electron spin resonance spectrometry.

 Findings: Brain water contents evaluated by the dry-wet weight method were increased at 1 hour and 48 hours after recirculation, which were demonstrated by ¹H-MRI. The superoxide scavenging activity showed a significant decrease at 45 minutes of recirculation and a significant increase at 12 hours of recirculation. The present modified model demonstrated that the mortality rates by 72 hours were 8.3% (15 minutes ischemia), 15.0% (30 minutes ischemia), and 42.9% (45 minutes ischemia), all of which were higher than that of the original method described by Pulsinelli et al.

 Interpretation: In conclusion, this modified four-vessel occlusion method gives a high level of success in producing reversible forebrain ischemia.