Cerebral cortical changes in acute experimental hypertension: An ultrastructural study

Area of Science:

• Neuroscience
• Pathology
• Vascular Biology

Background:

• Hypertensive encephalopathy is characterized by focal increases in brain vascular permeability.
• The relationship between this increased permeability, cerebral edema, and the underlying vascular mechanisms remains incompletely understood.

Purpose of the Study:

• To investigate if increased vascular permeability in hypertensive encephalopathy is linked to focal cerebral edema.
• To identify the specific tissue components involved in this edema.
• To elucidate the mechanism and vessel types responsible for increased blood-brain barrier permeability.

Main Methods:

• Utilized angiotensin-induced acute hypertension in a rat model.
• Employed horseradish peroxidase as a tracer to assess vascular permeability.
• Conducted quantitative morphometric studies at 90 seconds and 8 minutes post-hypertension onset.

Main Results:

• Significant perivascular glial swelling was observed around arterioles, venules, and capillaries in permeable areas.
• Horseradish peroxidase tracer was detected in arteriolar walls and surrounding neuropil, indicating extravasation.
• Enhanced endothelial pinocytosis was identified as the primary mechanism of increased permeability, particularly in arterioles, occurring rapidly after hypertension onset.

Conclusions:

• Increased vascular permeability in hypertensive encephalopathy is associated with focal perivascular glial swelling.
• Enhanced pinocytosis, rather than mechanical vessel damage, is the principal mechanism driving this permeability.
• Arterioles are the primary sites of this rapid, pinocytosis-mediated tracer extravasation.