6-hydroxydopamine and the blood-brain barrier in adult conscious rats

6-hydroxydopamine (6-OHDA), 15 or 50 mg . kg-1 given as bolus i.v. injection to adult conscious rats with aortic catheter, rapidly increased mean arterial pressure by 70-78 mmHg. The pressure returned to normal within 40-60 min. The cerebrovascular permeability in rats given 6-OHDA and sacrificed 10 or 60 min later was enhanced as indicated by extravasation of Evans blue albumin and significant increase of 125I human serum albumin content in brain tissue compared to control rats. When the increase in blood pressure was diminished by i.v. phentolamine, 6-OHDA treated rats did not differ from controls. It is concluded that the blood pressure elevation induced by i.v. 6-OHDA facilitates the entry of the drug into the brain parenchyma.