Effect of adrenergic blockade on autoregulation of the cerebral blood flow during orthostatic tests

Abstract

In experiments on rats under local anesthesia the action of phentolamine and propranolol on autoregulation of the cerebral blood flow (ACB) was studied during orthostatic tests (OT). The cerebral blood flow was measured in the carotid system, the venous pressure in the cerebral vessels, and the perfusion pressure in the carotid arteries; the resistance of the cerebral vessels was calculated. OT were simulated by tilting a special table with the animal (head upward or downward) through 40–80° from the horizontal plane. The results showed that adrenergic blockade in most cases of OT disturbed ACB: phentolamine led to a passive increase in the cerebral blood flow in response to an increase in perfusion pressure, whereas propranolol, on the other hand, caused a passive decrease in the cerebral blood flow in response to a fall of perfusion pressure.