New Insights Into Brain Damage in Stroke-Prone Rats

Abstract

Background and Purpose-The spontaneously hypertensive stroke-prone rat (SHRSP) is an animal model for a complex form of cerebrovascular pathology. MRI provides an efficient and noninvasive tool for studying the time course of brain damage. The aim of this study was to gain new insights into the pathological phenomena responsible for the occurrence of brain injury in SHRSP with the use of the apparent diffusion coefficient of water (ADC), one of the most efficient MRI parameters for detecting brain abnormalities. To this end, the pattern of ADC variation observed in SHRSP was compared with that of focal ischemia induced in both SHRSP and Sprague-Dawley rats. Methods-Four groups of animals were studied: SHRSP developing spontaneous brain lesions fed with a salt-loaded (nϭ15, group 1) or standard diet (nϭ3, group 2) and Sprague-Dawley rats (nϭ8, group 3) and SHRSP (nϭ8, group 4) with permanent middle cerebral artery occlusion. ADC maps and T2-weighted images of brains were performed by MRI. After the rats were killed, the brains were removed and histologically processed. Results-There was no decrease in ADC during spontaneous stroke in the SHRSP fed with a normal or salt-enriched diet, while both the SHRSP and Sprague-Dawley rats with middle cerebral artery occlusion showed a marked decrease that lasted for 24 to 48 hours. Conclusions-Cerebral ischemia cannot be considered a major factor in the onset of spontaneous brain lesions in SHRSP, which show only vasogenic edema after the beginning of the damage with no evidence of metabolic impairment. Key Words: animal models Ⅲ brain injuries Ⅲ diffusion Ⅲ magnetic resonance imaging Ⅲ middle cerebral artery occlusion Ⅲ rats T he spontaneous hypertensive stroke-prone rat (SHRSP) is generally considered a good experimental model for studying the hypertensive damage leading to stroke, 1,2 but the similarity between SHRSP and human stroke is still a matter of debate. 3,4 The model has been used to study vascular and brain tissue alterations both structurally and functionally, [5][6][7][8] and the relationship between histopathological findings and behavioral or metabolic abnormalities (eg, increased aggressiveness, hypokinesia or hyperkinesia, blood-brain barrier damage, proteinuria, a sudden loss of body weight) has also been extensively investigated. 1,9 -12 However, less information is available concerning the onset of the spontaneous brain damage and the mechanisms responsible for the development of brain abnormalities. 12 The morphological and histopathological investigations directed at the characterization of the brain lesion in SHRSP did not univocally clarify the pathogenesis of the damage. In fact, the term stroke is not univocally adopted in literature that concerns SHRSP studies, and there is ambiguity regarding whether this term is used to mean hemorrhage, infarct, or hemorrhagic infarct. 2,3,[5][6][7] This is in part due to the difficulty of precisely predicting the timing and the location of the spontaneous brain lesions, in turn making their systematic study i...

The Pathologic Cascade of Cerebrovascular Lesions in SHRSP: Is Erythrocyte Accumulation an Early Phase?

“…The cumulative appearance of microinfarcts in one brain region can induce expanded tissue necrosis ( Figure 5A) otherwise typical for occlusions of bigger brain vessels (macroangiopathy) or cerebral lesions of SHRSP fed a salt loaded diet with 1% NaCl added to their drinking water (Guerrini et al, 2002). The development of (vasogenic) edema illustrated by T2 sequences in MRI ( Figures 5A and 5D) further decreases CBF ( Figure 6B).…”

Hypoxia-Induced Neuroinflammatory White-Matter Injury Reduced by Minocycline in SHR/SP

“…We observed an increase in ADC in the untreated animals that was corrected with minocycline; increased ADC may be seen in vasogenic edema, which was seen as an increase in WM lesions in T2-weighted signal. 7,35 Fractional anisotropy is composed of radial and axial diffusivity. Untreated animals showed reduced FA, which could be explained by an increase in radial diffusivity secondary to loss of WM tissue integrity.…”

“…20 weeks. 35 A recent study showed that SHR/SP with JPD and added salt developed increased permeability before development of intracerebral bleeding. 37 We combined the JPD with occlusion of one carotid to accelerate the pathologic changes in the WM; we began the abnormal diet at the twelve rather than the sixth week, resulting WM damage that was generally seen before strokes.…”

The Interleukin-8 (IL-8/CXCL8) Receptor Inhibitor Reparixin Improves Neurological Deficits and Reduces Long-term Inflammation in Permanent and Transient Cerebral Ischemia in Rats

“…The ischemic volume was determined by trace of apparent diffusion coefficient maps (Tr(D)) computation as previously described (23,24). The progression of the ischemic damage was assessed over time using ANOVA for repeated measurements with lesion volume (evaluated by MRI) as dependent variable and the treatment as independent variable.…”