Correlation Between Extravasation and Alterations of Cerebrovascular Laminin and β-Dystroglycan Immunoreactivity Following Cryogenic Lesions in Rats

Abstract

The blood-brain barrier becomes "leaky" following lesions. Former studies revealed that following lesions the immunoreactivity of cerebrovascular laminin becomes detectable whereas that of β-dystroglycan disappears. These alterations may be indicators of glio-vascular decoupling that may result in the impairment of the blood-brain-barrier. This study investigates correlation between the post-lesion extravasation and the above-mentioned immunohistochemical alterations. Following cryogenic lesions, the survival periods lasted 5, 10, 30 minutes, 1 or 12 hours, or 1 day. Some brains were fixed immediately post-lesion. Immunofluorescent reactions were performed in floating sections. The extravasation was detected with immunostaining for plasma fibronectin and rat immunoglobulins. When the survival period was 30 minutes or longer, the area of extravasation corresponded to the area of altered laminin and β-dystroglycan immunoreactivities. Following immediate fixation some laminin immunoreactivity was already detected. The extravasation seemed to precede this early appearance of laminin immunoreactivity. The β-dystroglycan immunoreactivity disappeared later. When the extravasation spread into the corpus callosum, vascular laminin immunoreactivity appeared but the β-dystroglycan immunoreactivity persisted. It seems that extravasation separates the glial and vascular basal laminae, which results in the appearance of laminin immunoreactivity. The disappearance of β-dystroglycan immunoreactivity is neither a condition nor an inevitable consequence of the 2 other phenomena.

The First Postlesion Minutes: An In Vivo Study of Extravasation and Perivascular Astrocytes Following Cerebral Lesions in Various Experimental Mouse Models

“…The present investigations do not support an early withdrawal of the vascular astrocyte end-feet or any other conspicuous astroglial movement. Together with our previous ones, 5 they suggest that it may be the extravasation which separates the astroglial and vascular basal laminae evoking laminin immunoreactivity and “detaching” astrocytes.…”

“…Following cryogenic lesions, extravasation was observed in a few minutes. [1][2][3][4][5] In our experiments, the shortest available postlesion time until fixation was about 3 min. In these brains, extravasation was already detected around the vessels.…”

“…The detachment may have a role in the postlesion extravasation since the glio-vascular coupling has a basic importance in the maintenance of blood-brain barrier. 10,11 In our former experiments, 5 it was impossible to clarify whether a glio-vascular detachment preceded the extravasation because delay caused by fixation made the events of the first minutes inaccessible for investigation.…”

“…"Sham" cryogenic lesions, that is, applying the copper rod without dry ice were performed in a previous study. 5 They resulted in no considerable extravasation.…”

“…In these brains, extravasation was already detected around the vessels. 5 Signs indicating glio-vascular detachment were also observed: The cerebrovascular laminin immunoreactivity had become detectable and electron microscopic investigation revealed a separation of astroglial and vascular basal laminae. 5…”