2-Vessel Occlusion/Hypotension: A Rat Model of Global Brain Ischemia

Summary

Bilateral carotid occlusion coupled with systemic hypotension produces global brain ischemia in the rat, resulting in damage to the hippocampus with reproducible severity. Animal subjects are impaired with predictable patterns of brain damage, they recover expediently, and mortality rates are comparatively low.

Abstract

Cardiac arrest followed by resuscitation often results in dramatic brain damage caused by ischemia and subsequent reperfusion of the brain. Global brain ischemia produces damage to specific brain regions shown to be highly sensitive to ischemia ¹. Hippocampal neurons have higher sensitivity to ischemic insults compared to other cell populations, and specifically, the CA1 region of the hippocampus is particularly vulnerable to ischemia/reperfusion ².

The design of therapeutic interventions, or study of mechanisms involved in cerebral damage, requires a model that produces damage similar to the clinical condition and in a reproducible manner. Bilateral carotid vessel occlusion with hypotension (2VOH) is a model that produces reversible forebrain ischemia, emulating the cerebral events that can occur during cardiac arrest and resuscitation. We describe a model modified from Smith et al. (1984) ², as first presented in its current form in Sanderson, et al. (2008) ³, which produces reproducible injury to selectively vulnerable brain regions ^3-6. The reliability of this model is dictated by precise control of systemic blood pressure during applied hypotension, the duration of ischemia, close temperature control, a specific anesthesia regimen, and diligent post-operative care. An 8-minute ischemic insult produces cell death of CA1 hippocampal neurons that progresses over the course of 6 to 24 hr of reperfusion, while less vulnerable brain regions are spared. This progressive cell death is easily quantified after 7-14 days of reperfusion, as a near complete loss of CA1 neurons is evident at this time.

In addition to this brain injury model, we present a method for CA1 damage quantification using a simple, yet thorough, methodology. Importantly, quantification can be accomplished using a simple camera-mounted microscope, and a free ImageJ (NIH) software plugin, obviating the need for cost-prohibitive stereology software programs and a motorized microscopic stage for damage assessment.

Introduction

Brain damage as a consequence of cardiac arrest and stroke is a leading cause of death and long-term disability. While cardiopulmonary resuscitation for victims of cardiac arrest succeeds in restoring spontaneous circulation in about 70,000 patients per year in the US ^7,8 at least 60% of these patients subsequently die in the hospital as a result of extensive brain damage and only 3-10% of resuscitated patients can resume their former lifestyles ^9,10 . Clearly, understanding the mechanisms that lead to brain damage following global brain ischemia and designing therapeutic interventions to minimize neurologic trauma is of critical importance.

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Protocol

1. Preparation

All animal experiments must conform to institutional guidelines and receive approval by a respective animal care committee prior to initiation. All procedures presented here have been approved by the Wayne State University Institutional Animal Care and Use Committee and follow the guidelines on the ethical treatment of animals as put forth in the Guide for the Care and Use of Laboratory Animals and to the US Government Principles for the Utilization and Care of Vertebrate Animals Used in Testing, Research, and Training. Before beginning surgery, prepare necessary surgical material and a surgery recovery cage. This procedure is ....

Results

The 2VOH model of global brain ischemia/reperfusion causes neuronal death in the CA1 region of the hippocampus. Figure 2 represents the injury produced by 8 min of global brain ischemia, processed 14 days after reperfusion. Figures 2A and 2B compare the hippocampi from sham and post-ischemic brains, stained with Cresyl violet. Figure 2A shows a hippocampus from a sham-operated rat which exhibits normal morphology, including an intact CA1. Figure .......

Discussion

The model described here produces an ischemic insult to the brain that can occur as a result of cardiac arrest and resuscitation, providing an injury similar to that found in humans. This method for producing global brain ischemia is one of multiple protocols. We utilize this protocol foremost for its comparably low mortality rate, rapid recovery, and reproducible results. The cardiac arrest/resuscitation model is arguably the most clinically relevant model, however technically the most difficult to constantly rep.......

Materials

Name	Company	Catalog Number	Comments
			Material Name
5-0 VICRYL suture, reverse cutting	Ethicon	J391H
Scalpel, No.10	Swann-Morton	6601
Gauze Sponges	Fisher	22-362-178
18G x 1 ½ in needle	BD	305201
23G x 1 in needle	BD	305145
26 G x 3/8 in needle	BD	305110
18 G x 1 ¼ catheter	EXEL	26735
1 ml syringe	BD	309659
10 ml syringe	BD	309604
60 ml syringe	BD	309653
Surgilube	Henry Schein	1152666
.9% Saline, plastic IV bag	Henry Schein	1537468
Suture 3-0 Silk	Henry Schein	1007842
Puralube Ophthalmic Ointment	Henry Schein	3390017
Betadine	Henry Schein	6903564
Sterile Towel Drape	Moore Medical	14170
Polyethylene Tubing, 50	Intramedic	427411
Stopcock, 3 way	Smiths medical	MX9311L
			Drug Name
AERRANE (isoflurane)	Henry Schein	2091966
Mapap Liquid (Tylenol)	Major Pharmaceuticals	1556
Kedavet (ketamine)	Ketathesia Butney	NDC 50989-996-06
Butorphic (butorphanol)	Lloyd Labs	4881
Heparin	APP Pharmaceuticals	504011
			Chemical Name
Paraformaldehyde prills	Elecron Microscopy Sci.	19202
2-methylbutane	Sigma	270342
Cresyl Violet Acetate	Sigma	C5042
Sucrose	Sigma	S9378
			Software
ImageJ	NIH