Entry of [3H]norepinephrine, [125I]albumin and Evans blue from blood into brain following unilateral osmotic opening of the blood-brain barrier.

The blood-brain barrier in adult rats was opened unilaterally by infusing 1.58 M L (+)-arabinose in 0.9% NaCl solution into the internal carotid artery, via a catheter in the external carotid. The common carotid remained patent during the procedure. Osmotic barrier opening allowed entry into the brain of three intravascularly administered tracers--a visual tracer Evans blue (pulsely injected) and radioactive tracers [3H]norepinephrine (continuously infused) and [125I]albumin (pulsely injected). In osmotically perfused brain tissue, uptake of both 3H and 125I from blood was increased 2-5-fold above control, with maximal increases observed in the caudate nucleus, hippocampus and thalamus. In control brain regions, Evans blue and albumin remained intravascular, whereas norepinephrine was taken up, possibly by sympathetic nerve endings in cerebral vessels, as a function of blood plasma concentration and duration of exposure. The barrier closed within 4 h after intracarotid arabinose infusion, and barrier opening was not associated with edema as measured two days after infusion.