title: Postischemic cerebral microvascular responses to norepinephrine and hypotension in newborn pigs.
abstract: We examined the effects of 20 minutes' cerebral ischemia on cerebral microcirculatory responses to topical norepinephrine and systemic hypotension in three groups (sham-operated control, 2-3 hours postischemia, and 24 hours postischemia) of anesthetized newborn pigs equipped with closed cranial windows. Cerebral ischemia may eliminate the prostanoid vasodilator system from the cerebral circulation. Norepinephrine (10(-4) M) decreased pial arteriolar diameters similarly in all three groups (27%, 28%, and 21%, respectively), but only the sham-operated group exhibited pial arteriolar dilation in response to hypotension (28% at 33 mm Hg). Two-three and 24 hours after cerebral ischemia, hypotension decreased pial arteriolar diameters (21% and 17%, respectively). In sham-operated piglets, norepinephrine and hypotension increased cortical periarachnoid cerebrospinal fluid prostanoid concentrations. However, neither norepinephrine nor hypotension altered cerebral prostanoid production 2-3 or 24 hours after cerebral ischemia. Therefore, we conclude that after cerebral ischemia, autoregulatory pial arteriolar dilation in response to hypotension is absent, while vasoconstriction in response to norepinephrine is intact.
authors.affiliation: Department of Physiology and Biophysics, University of Tennessee, Memphis 38163.
authors.forename: C W
authors.initials: CW
authors.lastname: Leffler
authors.forename: D W
authors.initials: DW
authors.lastname: Busija
authors.forename: D G
authors.initials: DG
authors.lastname: Beasley
authors.forename: W M
authors.initials: WM
authors.lastname: Armstead
authors.forename: R
authors.initials: R
authors.lastname: Mirro
mesh_terms: D000287:Administration, Topical; D000818:Animals; D000831:Animals, Newborn; D001160:Arterioles / Q000187:drug effects / Q000503:physiopathology; D001794:Blood Pressure / Q000187:drug effects; D001923:Brain Chemistry; D002545:Brain Ischemia / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects; D007022:Hypotension / Q000503:physiopathology*; D007427:Intracranial Pressure / Q000187:drug effects; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology; D011466:Prostanoic Acids / Q000032:analysis / Q000096:biosynthesis; D013552:Swine; D013997:Time Factors; D014664:Vasodilation / Q000187:drug effects
chemical_list: D011466:Prostanoic Acids; D009638:Norepinephrine