Cerebral circulation and norepinephrine: relevance of the blood-brain barrier.
The systemic administration of norepinephrine has minimal effects on the cerebral circulation, perhaps due to blood-brain barrier mechanisms. To test hypothesis, the cerebrovascular effects of norepinephrine beyond the blood-brain barrier were studied in anesthetized baboons, Intraventricular norepinephrine (40 mug/kg) resulted in significant increases in cerebral blood flow (40%), cerebral oxygen consumption (21%), and cerebral glucose uptake (153%). Intracarotid hypertonic urea opens the blood-brain barrier by osmotic disruption; Consequent to hypertonic urea, the intracarotid infusion of norepinephrine, 50 ng/kg-min, significantly increase cerebral blood flow (49%), cerebral oxygen consumption (21%), and cerebral glucose uptake (76%), It appears probable that the cerebrovascular responses to norepinephrine are dependent on the integrity of the blood-brain barrier; It is likely that the increase in cerebral blood flow, associated with norepinephrine when it bypasses the barrier, is secondary to an increase in cerebral metabolism.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D005947:Glucose / Q000378:metabolism; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects; D010215:Papio / Q000502:physiology*; D014508:Urea / Q000494:pharmacology
D014508:Urea; D005947:Glucose; D009638:Norepinephrine