Responsiveness of Human Infant Cerebral Arteries to Sympathetic Nerve Stimulation and Vasoactive Agents

Abstract

Responses of segments of basilar and middle cerebral arteries of eight human infants to activation of perivascular nerves and to vasoactive drugs were studied using a resistance artery myograph. The infants ages ranged from 23 wk of gestation to 34 postnatal days. Neurogenic vasoconstriction occurred in all segments and at 8 Hz was 12.7 +/- 3.5% (11%) of tissue maximum and was blocked by phentolamine (10(-6) M). There was no evidence of a neurogenic dilator response. Catecholamine histofluorescence was seen in nerves in the adventitia at all ages studied. Norepinephrine ED50 was 7.6 +/- 1.8 x 10(-7) M, and its maximum effect was 43.1 +/- 5.7% of tissue maximum. Both neural and norepinephrine responses were greater than those of the proximal parts of adult human middle cerebral arteries obtained postmortem and surgically removed adult human pial arteries. Electron microscopy demonstrated that neural density at the adventitiomedial junction in the infant vessels was greater than in the pial arteries. Constrictor responses to serotonin and prostaglandin F2 alpha were minimal in the two infants of 23 and 24 wk of gestation but were clearly present in the older infants. Histamine and acetylcholine were potent vasodilators. Indomethacin potentiated agonist-induced contraction. In a limited number of trials angiotensin II, neuropeptide Y, caused contraction and bradykinin, relaxation. It is concluded that there is a quantitative similarity between the studied responses of infant cerebral artery segments and human pial arteries of similar diameter. However, sympathetic nerves may potentially play a more important role in the regulation of cerebrovascular tone in the infant compared with the adult, and during the gestational period examined these vessels possess an indomethacin-sensitive system that buffers agonist tone.

Endothelin-1 and endothelin receptors in the basilar artery of the capybara

“…These results also imply that such cells were involved in the regulatory processes of cerebral blood flow. In mammals, the large cerebral arteries, including the basilar artery, are usually the major contributors to the blood flow in the mammalian brain (Bevan et al 1998). This may be of particular importance following regression of the internal carotid artery in mature capybara (Reckziegel et al 2001).…”

Effects of angiotensin II on the cerebral circulation: role of oxidative stress

“…Studies of cerebral arteries, including those in humans, have found that Ang II produces vasoconstriction (Whalley et al, 1985, 1987; Toda et al, 1990; Bevan et al, 1998; Stenman and Edvinsson, 2004; Miller et al, 2005; Vincent et al, 2005; Faraci et al, 2006; De Silva et al, 2009; Amberg et al, 2010; Ahnstedt et al, 2011). Both genetic and pharmacological approaches have established that Ang II induces constriction of cerebral arteries via activation of AT1 receptors (Naveri et al, 1994; Stenman and Edvinsson, 2004; Faraci et al, 2006).…”

Cerebral Effects of Commonly Used Vasopressor-Inotropes: A Study in Newborn Piglets

“…Since premature [5] and sick infants [6] have increased blood-brain barrier permeability, direct cerebrovascular as well as cerebral effects of antihypotensive therapy seem possible [7]. Contribution of adrenergic mechanisms to cerebrovascular regulation may be relatively unique to the developing brain [8], [9]. Thus, understanding how commonly used vasopressor-inotropes affect cerebrovascular mechanisms is of major clinical relevance in newborn infants.…”