Brain blood flow, chlorpromazine (Thorazine) and its protective action against the toxicity of O₂ at high pressure

¹ Department of Physiology, University of Michigan, Ann Arbor, Michigan

The influence of Thorazine preparation of chlorpromazine on brain blood flow was studied in acute experiments by continuous direct recording (thermopile) in anesthetized (pentobarbital) dogs. Internal carotid injection of chlorpromazine (Thorazine) invariably increased brain blood flow promptly and sustained it for some time, with or without an attendant decrease in blood pressure. This is ascribed to a dilatatory action on vascular walls independent of antiepinephrine effects or adrenergic blockage of nervous influence. The carotid sinus and body are relatively insensitive to chlorpromazine (Thorazine) and are not essential to this response. Similar amounts intravenously injected failed to alter brain blood flow or respiration, but heavier doses increased respiration temporarily, probably due to a coincident transient decrease in blood pressure and flow and/or stimulation of reflexogenic zones. Brain blood flow was not significantly affected by intraperitoneal or intramuscular administration. The data provide no evidence that the protection against the toxicity of oxygen at high pressure by chlorpromazine (Thorazine) might be due to its hypotensive action and a presumptive consequential decrease in cerebral blood flow and oxygen supply to the CNS as previously suggested.