A Blood-Brain Barrier? Yes and No.

Document Type

Article

Publication Date

12-1-1983

Abstract

Ventriculo-cisternal perfusion of horseradish peroxidase (HRP) in the mouse brain has demonstrated that a brain-blood barrier exists at the microvascular endothelium in brain parenchyma but not in the median eminence of the hypothalamus. The brain-blood barrier is similar to the blood-brain barrier in that: tight junctions prevent the movement of protein between endothelial cells, HRP taken into the endothelial cells is directed to lysosomal dense bodies, and, contrary to the literature, a vesicular transendothelial transport of HRP from brain to blood does not occur under normal conditions. The endocytosis of ventricular injected HRP from the abluminal side of the endothelium is demonstrably less than the endocytosis of intravenous injected HRP from the luminal side; hence, the cerebral endothelium expresses a degree of polarity regarding the internalization of its cell surface membrane and extracellular protein. The passage of cerebrospinal fluid-borne or blood-borne HRP between some ependymal cells of the median eminence is not precluded by tight junctions. These patent extracellular channels offer a direct pathway for the exchange of substances between cerebrospinal fluid in the third ventricle and fenestrated capillaries in the median eminence.

Publication Title

Proceedings of the National Academy of Sciences of the United States of America

Volume

80

Issue

23

First Page

7352

Last Page

7356

PubMed ID

6580650

Comments

The published version is available at: http://www.pnas.org/content/80/23/7352.short

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