Premium
Cytoprotection does not preserve brain functionality in rats during the acute post‐stroke phase despite evidence of non‐infarction provided by MRI
Author(s) -
Reese Torsten,
Pórszász Robert,
Baumann Diana,
Bochelen Damien,
Boumezbeur Fawzi,
McAllister Kevin H.,
Sauter André,
Bjelke Börje,
Rudin Markus
Publication year - 2000
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/1099-1492(200010)13:6<361::aid-nbm654>3.0.co;2-c
Subject(s) - somatosensory system , medicine , cortex (anatomy) , forelimb , somatosensory evoked potential , functional magnetic resonance imaging , isradipine , stroke (engine) , stimulation , diffusion mri , neuroscience , magnetic resonance imaging , psychology , anesthesia , anatomy , radiology , calcium , dihydropyridine , mechanical engineering , engineering
In animal models of stroke the promise of a therapy is commonly judged from infarct size measurements, assuming that a reduction in infarct size results in reduction of the functional deficits. We have evaluated the validity of the concept that structural integrity translates into functional integrity during the acute post‐stroke period (24 h). Unilateral permanent middle cerebral artery occlusion (pMCAO) in Fischer F344 rats leads to infarcts comprising the ipsilateral striatum and cortical structures, including the somatosensory cortex. Infarct volumes were assessed using magnetic resonance imaging (MRI) methods ( T 2 , diffusion, perfusion MRI). The functional integrity of the somatosensory cortex was assessed by functional MRI (fMRI) measuring changes in local cerebral blood volume, and by assessing the forelimb grip strength and the beam‐walking performance of the animals. Treatment with the calcium antagonist isradipine (2.5 mg/kg injected s.c. immediately after pMCAO) reduced the total infarct size by more than 40% compared to vehicle‐injected controls. In particular, the ipsilateral somatosensory cortex appeared normal in diffusion‐ and T 2 ‐weighted MRI images. In sham‐operated rats simultaneous electrical stimulation of both forepaws led to similar activation of both somatosensory cortices, while in pMCAO animals given vehicle only the contralateral cortex showed an fMRI response. Similarly, in pMCAO rats treated with isradipine, functional activation following bilateral electrical stimulation was only detected in the contralateral somatosensory cortex despite the normal appearance of the ipsilateral cortex in MRI images. Furthermore, fMRI responses to pharmacological stimulation with bicuculline were virtually absent in the ipsilateral somatosensory cortices both in vehicle‐ and isradipine‐treated rats. Finally there was no significant difference between vehicle‐ and isradipine‐treated animals upon the performance of beam‐walking test or in forelimb grip strength. It is concluded that during the acute (24 h) post‐occlusion period, structural integrity in the somatosensory cortex revealed by MRI does not translate into preservation of function. Copyright © 2000 John Wiley & Sons, Ltd. Abbreviations used: ADC apparent diffusion coefficientATP adenosine triphosphateBOLD blood oxygen level dependentCBF cerebral blood flowCBV cerebral blood volumeDW diffusion weightedFOV field‐of‐viewfMRI functional magnetic resonance imagingMRI magnetic resonance imagingNA number of averagesPET positron emission tomographypMCAO permanent middle cerebral artery occlusionRARE rapid acquisition with relaxation enhancements.c. subcutaneouslySW spectral widthTE echo delayTR repetition delayT 2 W T 2 ‐weighted.