Neonatal 6-hydroxydopamine treatment increases the vulnerability of the blood-brain barrier to acute hypertension in conscious rats.

Acute hypertension increases the cerebrovascular permeability to protein to a higher extent in anesthetized than in conscious rats. When hypertension is combined with a pronounced cerebral vasodilatation, e.g. in bicuculline-induced seizures, the protein leakage is enhanced. Conscoius, unrestrained 2--3-months-old rats received adrenaline or bicuculline i.v. during continuous recording of the mean arterial pressure and were killed 3 minutes later. Rats, neonatally sympathectomized by 6-hydroxydopamine, had significantly increased extravasation of 125I serum albumin in the brain after adrenaline-induced hypertension than nonsympathectomized rats. Since transection of the cervical sympathettic trunk alone does not have the same effect, a protection of the blood-brain barrier in acute hypertension in conscious rats may, at least in part, be mediated via the central noradrenergic innervation of cerebral vessels. Bicuculline did not increase blood pressure in 6-OHDA treated rats; thus the blood-brain barrier remained intact.