Chronic effects of osmotic opening of the blood-brain barrier in the monkey.

In the monkey, the blood-brain barrier and the blood-aqueous and blood-vitreous barriers of the eye can be opened by internal carotid perfusion of solutions of 2 molar urea in a way compatible with survival and, in some few cases, without detectable neurological deficits. Urea presumably acts by osmotically shrinking the endothelial cells of the cerebrovascular vessels and opening their tight junctions. The high incidence of brain necrosis with neurological sequelae after perfusion of urea by the present technique precludes the use of osmotic opening of the blood-brain barrier for pharmacotherapy at this time.