title: Intrinsic tone of cerebral artery segments of human infants between 23 weeks of gestation and term.
abstract: Segments of basilar and middle cerebral arteries of eight human preterm and early postnatal infants have been examined using the resistance artery myograph technique for wire-mounted segments and the pressure perfusion arteriograph. Myograph-mounted segments spontaneously developed tone of varying duration and time course. Perfused segments showed maintained tone levels of approximately 40% of maximum possible constriction when the intraluminal pressure was 60 mm Hg. This level is not different from that found in adult human pial arteries of similar lumen diameter. Indomethacin (10[-5] M) either initiated tone increase or potentiated existing tone in the isometrically mounted segments. After washout of vasoconstrictors norepinephrine (10[-6] M) and angiotensin II (10[-8] M), indomethacin caused a pronounced, long lasting increase in basal tone. Spontaneous tone was reversed by acetylcholine (10[-6] M), isoproterenol (10[-8] to 10[-5] M), histamine (10[-8] to 10[-5] M), and papaverine (10[-5] M). Low levels of tone were increased and higher levels decreased by intraluminal flow. The pressure/diameter curves of these vessels were of similar shape as those of the equivalent size in the adult. It is concluded that intrinsic tone is a prominent feature of these large cerebral arteries, and it is modified by an endogenous indomethacin-sensitive process.
authors.affiliation: Department of Pharmacology, College of Medicine, University of Vermont, Burlington 05405, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Bevan
authors.forename: E
authors.initials: E
authors.lastname: Vijayakumaran
authors.forename: A
authors.initials: A
authors.lastname: Gentry
authors.forename: T
authors.initials: T
authors.lastname: Wellman
authors.forename: J A
authors.initials: JA
authors.lastname: Bevan
mesh_terms: D001921:Brain / Q000098:blood supply* / Q000196:embryology; D002536:Cerebral Arteries / Q000196:embryology* / Q000502:physiology*; D004594:Electrophysiology; D005314:Embryonic and Fetal Development; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D014661:Vasoconstriction / Q000502:physiology*