Cerebrovascular ultrastructural alterations after intra-arterial infusions of ouabain, scilla-glycosides, heparin and histamine.

Cardiac glycosides which inhibit Na/K-ATPase (ouabain, scilliroside, scillirosidin) as well as heparin and histamine were infused into a cannulated branch of the middle cerebral artery or by isolated head perfusion in cats and dogs. Ouabain permeating the blood-brain barrier (BBB) caused the same selective swelling of astrocytes and of certain presynaptic elements as after direct application to the brain tissue. The other cellular elements of brain tissue and the vascular endothelium did not react, although the latter was exposed to the highest drug concentrations (about 10-3 M ouabain). By the swelling about one third of the capillaries became more or less constricted accompanied by an increase in endothelial vesiculation and in the number of osmiophilic inclusions in all cells of the vascular wall and of the pericapillary tissue. Osmiophilic material resembling plasma proteins occured in widened intercellular clefts indicating an increased BBB permeability after survival times (40 min). In contrast to the capillaries some terminal vessels are dilated which may correspond to shunt vessels causing an inhomogeneous, even increased cerebral blood flow after ouabain. Scilliroside and scillirosidin cause essentially the same changes as ouabain, but of smaller intensity and extent. In the present study, neither histamine nor heparin caused any structural change of the vessels or brain tissue.