Autonomic and pharmacological control of oxygen autoregulation mechanisms in brain tissue

The effect of several agents active on autonomic nervous system functions was tested on brain oxygen autoregulation parameters. It was found that atropine, propranolol and isproterenol had no influence on the measured parameters. Phenoxybenzamine, tolazoline and dibenamine all suppress autoregulation. In an additional experimental series, a phenoxybenzamine infusion was given during O2 breathing. The infusion induced a marked rise in TpO2. It is concluded that an alpha-adrenergic mechanism is part of the autoregulation process, and its pharmacological blockade could be used to raise TpO2 levels in brain with O2 breathing at normal atmospheric pressure. Also, the increase in brain TpO2 induced by 95% O2 - 5% CO2 breathing seems to be blocked by alpha-adrenolytic drugs.