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Quantitative evaluation of blood-brain barrier permeability following middle cerebral artery occlusion in rats
1Department of Neurology, University of Miami School of Medicine, FL 33101, USA.
Abstract:
A sensitive quantitative fluorescence method was used to explore the time course and regional pattern of blood-brain barrier (BBB) opening after transient middle cerebral artery occlusion (MCAo). Male Sprague-Dawley rats were anesthetized with halothane and subjected to 2 h of temporary MCAo by retrograde insertion of an intraluminal nylon suture, coated with poly-L-lysine, through the external carotid artery into the internal carotid artery and MCA. Damage to the BBB was judged by extravasation of Evans Blue (EB) dye, which was administered either 2, 3, 24 or 48 h after onset of MCAo. Fluorometric quantitation of EB was performed 1 or 2 h later in six brain regions. Cerebral infarction volumes were quantitated from histopathological material at 72 h. EB extravasation first became grossly visible in the ipsilateral caudoputamen and neocortex following 3 h of MCAo, was grossly unapparent at 24-26 h, and was maximal at 48-50 h. Fluorescence quantitation confirmed that BBB opening was absent at 2-3 h but present at all later times. In the hemisphere ipsilateral to MCAo, a 179% mean increase in extravasation of EB (compared to sham rats) was measured at 4 h, 407% at 5 h, 311% at 26 h and 264% at 50 h. (in each case, P < 0.05 vs. sham). The volume of infarcted tissue at 72 h in this model was 163.6 +/- 7.7 mm3. Our results indicate that an initial, acute disruption of the BBB occurs between 3 and 5 h following MCAo, and that a later, more widespread increase in regional BBB permeability is present at 48 h. Regional measurement of Evans Blue extravasation offers a precise means of quantitating BBB disruption in focal cerebral ischemia; this method will be of considerable utility in assessing the BBB-protective properties of pharmacological agents.
Insights
Blood-brain barrier (BBB) opening after middle cerebral artery occlusion (MCAo) in rats shows an initial acute disruption between 3-5 hours and a later, widespread increase in permeability by 48 hours. This study quantifies BBB damage in focal cerebral ischemia.
Area of Science:
- Neuroscience
- Cerebrovascular Research
- Ischemic Stroke Models
Background:
- The blood-brain barrier (BBB) integrity is crucial for brain function.
- Disruption of the BBB is a hallmark of ischemic stroke, contributing to secondary brain damage.
- Understanding the temporal dynamics of BBB opening is vital for developing effective stroke therapies.
Purpose of the Study:
- To investigate the time course and regional pattern of BBB opening following transient middle cerebral artery occlusion (MCAo) in a rat model.
- To quantitatively assess BBB disruption using Evans Blue (EB) extravasation and fluorescence measurements.
- To correlate BBB opening with infarct volume in focal cerebral ischemia.
Main Methods:
- Transient middle cerebral artery occlusion (MCAo) was induced in Sprague-Dawley rats for 2 hours.
- Evans Blue (EB) dye was administered at 2, 3, 24, or 48 hours post-MCAo.
- EB extravasation was quantified fluorometrically in six brain regions 1-2 hours after dye administration.
- Cerebral infarct volumes were determined histopathologically at 72 hours.
Main Results:
- Gross BBB opening was first observed in the ipsilateral caudoputamen and neocortex at 3 hours post-MCAo, maximal by 48-50 hours.
- Quantitative fluorescence confirmed BBB opening was absent at 2-3 hours but present later.
- Significant increases in EB extravasation were noted at 4, 5, 26, and 50 hours post-MCAo compared to sham rats (P < 0.05).
- The average infarct volume at 72 hours was 163.6 ± 7.7 mm³.
Conclusions:
- An initial, acute BBB disruption occurs between 3 and 5 hours after MCAo.
- A later, more widespread increase in BBB permeability is evident by 48 hours post-MCAo.
- Regional EB extravasation measurement provides a precise method for quantifying BBB disruption in focal cerebral ischemia, useful for evaluating BBB-protective agents.