| PART I: Improved Model of Middle Cerebral Artery OcclusionCerebral vascular disease now is becoming the third most common disease-related killer in our society. Cerebral ischemia is a severe disease with high mortality and disability. Most survivors have neurological impairment at different degrees. Desirable animal models are those that replicate features of human cerebrovascular syndromes. The development of reliable and reproducible animal models of cerebral ischemia is required for the systematic study the pathophysiology and treatment of stroke. Rat models of focal cerebral ischemia have gained increasing acceptance in recent years owing to their relevance to the human clinical setting. Middle cerebral artery occlusion (MCAo )in the rats has been in use since 1975.This technique is invasive and does not permit reperfusion. In 1986,Koizumi et al reported a novel and relatively noninvasive method of achieving reversible MCAo by using of an intraluminal suture. Zea Long et al improved it. But, the infarct volume and distribution used those methods are inconsiderable. We then chose to coat the sutures with poly-L-lysine for intraluminal MCAo, in order to increase the adhesive forces around the suture. Then we assessed the success of MCAo by both infarct volume and neurological evaluation.Objective: To evaluate a modified method of intraluminal suture occlusion of the middle cerebral artery on the neurobehavioral function and on the volume of brain infarction in rats subjected to a temporary focal cerebral ischemic insult.Method: Sprague-Damley rats were subjected to 2 hour temporary MCA occlusion (MACO) with poly-L-lysine coated suture (0.1%) and conventional suture .Model of Focal Ischemia: Focal cerebral ischemia was induced by using a minor modification of the endovascular internal carotid artery suture method developed by Longa et al. In brief, after an intraperitoneal injection of 4% chloralhydrate, the right common carotid artery (CCA) was exposed through a midline neck incision and was carefully dissected free from surrounding nerves and fascia, from its bifurcation to the base of the skull. The right common carotid artery was exposed at its bifurcation by a midline cervical incision. The branches from the external carotid artery (ECA) were coagulated, The ECA was then transected, and a 4-0 nylon monofilament suture (with its tip rounded by heating) was inserted into the ECA stump. To occlude the origins of the MCA and proximal anterior cerebral artery, the suture was advanced into the internal carotid artery (ICA) fora distance of 18-20 mm beyond the internal carotid artery (the pterygopalatine artery bifurcation) and the wound was closed. The monofilament was removed 60 after occlusion. The animals were allowed food and water ad libitum. Behavioral motor functions were evaluated at 180 minutes, 24 hour, 48 hour and 72 hour after reperfusion by eight-point behavioral rating scale and postural reflex. Brains were perfusion-fixed and infarct volumes were measured at the time of 72 hours after reperfusion.Calculation of the Infarct VolumeThe rats were then killed, and the brains were quickly removed, inspected to confirm appropriate placement of the intraluminal occluder, and sectioned coronally into six slices each with a 2-mm thickness. The six brain slices were stained with TTC, Areas ipsilateral to the occlusion not stained red with TTC were recorded as infracted, and the areas of the uncorrected infarcted area and the total areas of both hemispheres were calculated for each coronal slice.The uncorrected infarct volume in the cortex and caudoputamen was calculated by multiplying the area by the slice thickness and summing the volume. The results were compared between two groups.Results: 9 of 20 rats with uncoated suture had infarct. While in the group with poly-L-lysine-coated suture, 15 of 20 rates had infarct. Our results demonstrate a liner relationship between motor functional impairment and lesion volumes. Infarct volumes were significantly larger in rats with poly-L-lysine-coated s...
|
PDF Full Text Request