Vascular permeability in the area postrema and hypothalamus

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Abstract
Vascular permeability in the region of the area postrema and the hypothalamus was studied with iodinatedproteins. The border zone of the area postrema and the nucleus infundibular is exhibit increasedpermeability as compared with the other parts of the brain. This increasedpermeability couldbe demonstrated with radioactive albumin, but not with radioactive globulin. Under the conditions of postmortemperfusion, the part of the medulla bordering the area postrema and the nucleus infundibular is did not show increased permeability. This is interpreted as indicating that increased permeability of these regions must depend on the presence of metabolic processes which are present only during life. On the contrary, the increased permeability of the area postrema proper and of the infundibular stalk was present in postmortem perfusion. It is concluded from these experiments and from the results obtained after exchange perfusion with dextran, that the mechanism of increased vascular permeability of the nucleus infundibular is and the border zone of the area postrema is different from that of the infundibulum and the area postrema proper. It is suggested that the nucleus infundibular is and the border zone of the area postrema should be singled out as parts of the central nervous system which exhibit specific vascular permeability. In this respect, they differ both from the rest of the central nervous system and from these regions which are recognized as not having the blood-brain barrier.