Elsevier

Brain Research

Volume 1246, 30 December 2008, Pages 158-166
Brain Research

Research Report
A modified suture technique produces consistent cerebral infarction in rats

https://doi.org/10.1016/j.brainres.2008.08.096Get rights and content

Abstract

Intraluminal occlusion of the middle cerebral artery (MCA) is used extensively in cerebral ischemia research. We tested a modified nylon suture in a rat model of middle cerebral artery occlusion (MCAO) under two anesthesia regimens. Sprague–Dawley rats were divided into six groups (Group 1, Poly-l-lysine-coated suture under ketamine/xylazine anesthesia; Group 2, modified suture under ketamine/xylazine anesthesia; Group 3, Poly-l-lysine-coated suture under ketamine/xylazine anesthesia with mechanical ventilation; Group 4, modified suture under ketamine/xylazine anesthesia with mechanical ventilation; Group 5, Poly-l-lysine-coated suture under isoflurane anesthesia; Group 6, modified suture under isoflurane anesthesia) and subjected to 2-hour MCAO. Regional cerebral blood flow (rCBF) was monitored by Laser-Doppler flowmetry. Neurological evaluation and ischemic lesion (TTC stain) were assessed at 24 hours of reperfusion. The total ischemic lesion (sum of areas with lacking and intermediate TTC staining) was similar among all six groups. Compared with a Poly-l-lysine-coated suture technique, the modified suture technique produced a lower rCBF, larger infarct size, smaller variance of infarct size, and greater neurological deficit. In addition, isoflurane significantly reduced infarct size. We conclude that the use of this modified suture technique with ketamine/xylazine anesthesia and mechanical ventilation produces a more consistent change in cerebral ischemic damage following MCAO in rats.

Introduction

Ischemic stroke is a leading cause of mortality and long-term disability. Recently, recanalization with drugs during acute ischemic stroke have been shown to be clinically effective for treating ischemic stroke (Smith, 2007). Thus, a reliable animal model of transient focal ischemia is becoming more important in order to study the pathophysiology of ischemic stroke and evaluate new therapeutic approaches. Intraluminal occlusion of the middle cerebral artery (MCA) in rats using a suture methodology was first described by Koizumi et al., and has been extensively applied and studied due to its minimal invasiveness (Koizumi et al., 1986). Due to the variability in the final infarct size this method has been modified by many investigators (Bouley et al., 2007); (Longa et al., 1989); (Palmer et al., 2001); (Shimamura et al., 2006); (Wegener et al., 2005); (Woitzik et al., 2006). Previous studies have demonstrated that rat strain, animal age, blood pressure, brain temperature, blood glucose, suture type, and site of filament insertion are factors contributing to the variability in the final infarct size (Bouley et al., 2007). However, we suggest that anatomical variations of the origin of the MCA might be a primary factor resulting in a difference in blood flow interdiction of the MCA supplying area during middle cerebral artery occlusion (MCAO), and finally a difference in ischemic brain damage (Hartkamp et al., 1999); (Stock et al., 1996). In this study, we used a modified suture technique to produce a more complete and consistent blood flow interdiction of the MCA supplying area for any variation of MCA origination. Thus, our first goal was to compare the effect of a Poly-l-lysine-coated suture technique and our modified suture technique on transient focal ischemia-induced brain damage and cerebral blood flow.

Anesthesia also may be an important factor affecting infarct size in a MCAO model. Several anesthetics including ketamine, urethane, chloral hydrate, ether, halothane, and isoflurane have being used in a MCAO rat model (Butcher et al., 1993); (Longa et al., 1989); (Matucz et al., 2004); (Ridenour et al., 1991); (Warner et al., 1991); (Xu et al., 2003). However, anesthetics, especially volatile anesthetics, have been shown to temporally reduce ischemic cerebral injury during the early stage of reperfusion (Head and Patel, 2007); (Kapinya et al., 2002). In addition, isoflurane was recently reported to provide protection against transient focal ischemia (Sakai et al., 2007). Thus, our second goal was to compare the effect of ketamine/xylazine and isoflurane on transient focal ischemia-induced brain damage.

Section snippets

Physiological parameter

The physiological parameters measured immediately before MCAO are summarized in Table 1. There was no significant difference in mean arterial blood pressure (MABP), heart rate (HR), or arterial blood gas (pH, PCO2, and PO2) between the Poly-l-lysine-coated suture group and the modified suture group regardless of the anesthesia method. In addition, no significant difference was observed in MABP among all six groups. Anesthesia with ketamine/xylazine induced a respiratory acidosis in groups 1 and

Discussion

There are several new findings in the present study. First, our modified silicon-coated suture produced a larger infarct size, smaller variance of infarct size, and greater neurological deficit than the Poly-l-lysine-coated suture method in a rat transient MCAO model. In addition, a lower rCBF at MCAO onset and during MCAO was found in the modified suture groups. Second, mechanical ventilation prevented ketamine/xylazine-induced respiratory acidosis, but did not affect the final infarct size

Experimental groups

All procedures were in accordance with the “Principle of Laboratory Animal Care” (NIH publication No. 86-23, revised 1985) and were approved by the Institutional Animal Care and Use Committee. Male Sprague–Dawley rats (body weight 380–420 g) were purchased from Harlan and assigned to one of six groups. Group 1 (n = 10): Poly-l-lysine-coated suture under ketamine/xylazine (80 mg/kg IP, 40 mg/kg IP for supplement as needed) anesthesia. Group 2 (n = 8): Modified suture under ketamine/xylazine

Acknowledgments

This study was supported by National Institutes of Health Grants DA 14258, HL79587, AA 11288, a Scientist Development Grant from the American Heart Association (0635052N), and funds from the University of Nebraska Medical Center.

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