Induction of Focal Cerebral Ischemia by Continuous Recording of Cerebral Blood Flow Using Laser Doppler Flowmeter in Rat

Ischemic stroke is the third leading cause of death and disability in most of the human societies. There is no effective treatment due to complexity of the pathophysiological mechanisms. Today, more researches are designed to introduce involving factors and new treatment strategies in brain ischemia. The objective of this study is to introduce an experimental model of the focal cerebral ischemia in rat with increased success rate and low mortality rate. In this research 32 male rats (Sprague-Dawley) were studied as in four experimental groups. Animals were anesthetized with chloral hydrate (400mg/kg, ip). Focal cerebral ischemia was induced by intraluminal filament method. A silicon coated nylon filament was used for middle cerebral artery occlusion. Regional cerebral blood flow was monitored by laser Doppler flowmetery to guide the insertion of the filament into the vascular pathway. 24 hours after ischemia (90minutes), animals were assessed for neurological outcome, infarct volume and brain edema formation. A new and reformed neurological test was used for evaluation of neurological deficits. 2 - millimeter coronal sections were collected from 6 levels of the brain and stained, digitized and quantified by using an image analysis system. Ischemic brain edema formation was investigated by brain water content detection. Induction of ischemia in ischemic group, seriously caused impairment of motor functions (neurological deficit score 4±0.5) While sham operated rats had no motor deficit and infarction. Mean total infarct volume of left (ischemic) hemisphere was 402±43 mm3 and 62.7 percent of infarction occurred in cortical regions of the brain. Induction of focal cerebral ischemia in the left (ischemic) hemisphere of the brain significantly increased water content (84±0.23 percent) compared to both hemispheres of sham group and right hemisphere of the same group. Success rate of ischemia induction was 100 percent and there was no mortality due to technical problems. Our findings indicate that continuous recording of regional cerebral blood flow using laser Doppler flowmeter had significant role in increasing success rate and lowering mortality rate in the present model of ischemic rat. This experimental model with high success rate and low limitation can be used for brain ischemia studies and evaluating new therapeutic strategies.