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

The effect of phentolamine and anapriline on the cerebral blood flow autoregulation (CBFA) under the orthostatic test (OT) was studied in experiments on locally anesthetized rabbits. Cerebral blood flow (CBF) in the carotids, venous pressure in the cerebral vessels, perfusion pressure (PP) in the carotid arteries were measured, the resistance of cerebral vessels was calculated. OT was modeled by tilting a special table with the animal (with its head upwards or a special table with the animal (with its head upwards or downwards) by 40--80 degrees from the horizontal level. The results showed adrenergic block in most of OT cases to disturb CBFA; phentolamine promoted passive increase of CBF when PP was increased; on the contrary, anapriline promoted passive CBF reduction when PP was decreased.