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Penumbral microcirculatory changes associated with peri-infarct depolarizations in the rat.

AbstractBACKGROUND AND PURPOSE:
This study was designed to investigate the influence of peri-infarct depolarization elicited by occlusion of the middle cerebral artery on the dynamics of the microcirculation.
METHODS:
The microcirculation in the frontoparietal cortex of 9 rats was visualized in real time through a closed cranial window with the use of laser-scanning confocal fluorescence microscopy combined with intravenous fluorescein isothiocyanate (FITC)-dextran and FITC-labeled erythrocytes. The direct current potential/electrocorticogram was continuously monitored. Intraluminal focal ischemia was induced for 2 hours in 6 rats anesthetized with halothane and mechanically ventilated. Reperfusion was monitored for 1 hour. Three rats underwent sham operation. Brains were removed 24 hours after occlusion and processed for histology.
RESULTS:
In control conditions, the velocity of fluorescent erythrocytes through capillaries was 0.51+/-0.19 mm/s (mean+/-SD), and the diameter of the arterioles studied was 33+/-12 microm. Under ischemia, erythrocyte velocity through capillaries was significantly decreased to 0.33+/-0.14 mm/s, while arteriole diameter did not change significantly. During spontaneous peri-infarct depolarizations, arteriole diameter was significantly increased (119+/-23% of baseline), while capillary erythrocyte velocity was further decreased by 14+/-34%. The direction of arteriolar blood flow episodically and transiently reversed during approximately half of the peri-infarct depolarizations. The decrease in capillary erythrocyte velocity was more pronounced (23+/-37%) in these cases. After reperfusion, the microcirculatory variables rapidly returned to baseline. All rats in the ischemic group had infarcts 24 hours after occlusion.
CONCLUSIONS:
Peri-infarct depolarization has an adverse influence on penumbral microcirculation, reducing capillary perfusion by erythrocytes, despite dilatation of arterioles. These findings suggest that a steal phenomenon contributes to the deleterious effect of these depolarizations.
AuthorsElisabeth Pinard, Hélène Nallet, Eric T MacKenzie, Jacques Seylaz, Simon Roussel
JournalStroke (Stroke) Vol. 33 Issue 2 Pg. 606-12 (Feb 2002) ISSN: 1524-4628 [Electronic] United States
PMID11823677 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Dextrans
  • fluorescein isothiocyanate dextran
  • Fluorescein-5-isothiocyanate
Topics
  • Animals
  • Arterioles (pathology, physiopathology)
  • Blood Flow Velocity
  • Cerebral Cortex (blood supply, pathology, physiopathology)
  • Cerebral Infarction (pathology, physiopathology)
  • Cerebrovascular Circulation
  • Cortical Spreading Depression
  • Dextrans
  • Electroencephalography
  • Erythrocytes (chemistry, cytology)
  • Fluorescein-5-isothiocyanate (analogs & derivatives, chemistry)
  • Infarction, Middle Cerebral Artery (pathology, physiopathology)
  • Male
  • Membrane Potentials
  • Microcirculation (pathology, physiopathology)
  • Microscopic Angioscopy
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Rats
  • Rats, Sprague-Dawley
  • Vascular Patency

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