Postjunctional Alpha(2)-Adrenoceptors in Pial
Arteries of Anesthetized Newborn Pigs

Busija, David W.; Leffler, Charles W.

doi:10.1159/000457726

Cited by 34 publications

(9 citation statements)

References 17 publications

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“…However, NE constriction of rat aorta was completely reversed by nanomolar concentrations of ANF. The lack of an effect of ANF on NE constriction of small cerebral arteries might be explained by the recent observations that small pial arteries may possess predominantly a 2 -adrenoceptors, 52 together with our present evidence for the lack of effect of ANF on a 2 -constriction. Rat aorta is known to possess only a i -adrenoceptors.…”

Section: Relation Of Present Results To In Vitro Literaturesupporting

confidence: 72%

Microvascular effects of atrial natriuretic factor: interaction with alpha 1- and alpha 2-adrenoceptors.

Faber

Gettes

Gianturco

1988

Circulation Research

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The cremaster skeletal muscle of anesthetized rats was denervated and extended with intact circulation into a tissue bath. Intravital microscopy was used to measure microvessel diameter at three different anatomical levels within the microcirculation: large distributing arterioles (x control diameter = 100 +/- 7 micron), large capacitance venules (147 +/- 8 micron), and small terminal arterioles (17 +/- 1 micron). Norepinephrine (NE) was added to the cremaster bath to produce intermediate reductions in diameter of large arterioles and venules (55% and 38% of maximum constriction, respectively). In the presence of NE tone, bath-added atrial natriuretic factor (ANF) produced concentration-dependent dilation of both arterioles and venules. Arteriolar IC25 = 18 pmol and IC50 = 1.2 X 10(-10) M; venules exhibited similar sensitivity. However, the highest ANF concentration examined (10(-7) M) only reversed NE-induced tone by 70%. In a second large vessel group ANF completely reversed constriction induced by the alpha 1-adrenoceptor agonist, phenylephrine, in the presence of 5 X 10(-7) M yohimbine. However, vessels constricted with the alpha 2-receptor agonist UK-14,304 (in the presence of 10(-8) M prazosin) were insensitive to ANF. A third group of terminal arterioles, which possess considerable spontaneous "intrinsic" tone, were studied in the absence of alpha-receptor agonists. Significant dilation occurred at greater than 10(-7) M, and the maximal response was only 25% of complete dilation with adenosine. These data indicate that ANF exhibits a high potency and selectivity for reversal of alpha 1-adrenoceptor-mediated constriction of large arterioles and venules. Constriction produced by alpha 2-adrenoceptor occupation or by nonadrenergic "intrinsic" mechanisms appears to be insensitive to ANF. We propose that the ability of ANF to reduce microvascular resistance depends on the relative contribution of alpha 1-, alpha 2-, and intrinsic vasoconstrictor components to the prevailing level of smooth muscle tone. Differences in these components among regional circulations and between arterial and venous smooth muscle may contribute to the systemic hemodynamic pattern produced by ANF.

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Section: Relation Of Present Results To In Vitro Literaturesupporting

confidence: 72%

Microvascular effects of atrial natriuretic factor: interaction with alpha 1- and alpha 2-adrenoceptors.

Faber

Gettes

Gianturco

1988

Circulation Research

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“…␣ 2 -Adrenergic receptors are widely distributed within the cerebral vasculature (18,33). Much work on the adrenergic regulation of the cerebral circulation has focused on the extrinsic sympathetic innervation of arteries and pial vessels.…”

Section: Neurophysiological Effects Of Dex Cerebral Blood Flow and Mementioning

confidence: 99%

Dexmedetomidine for Neurological Surgery

Bekker¹,

Sturaitis²

2005

Operative Neurosurgery

173

171

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Dexmedetomidine is a new intravenous drug gaining popularity in neuroanesthesia and neurocritical care practice. This alpha2-adrenergic receptor agonist offers a unique "cooperative sedation," anxiolysis, and analgesia with no respiratory depression. Cerebral effects are generally consistent with a desirable neurophysiological profile, including neuroprotective characteristics. In addition, sympatholytic and antinociceptive properties allow for hemodynamic stability at critical moments of neurosurgical stimulation. This review will address the neuropharmacology and neurophysiology of alpha2-adrenergic agonists and will specifically consider the rapidly evolving applicability of dexmedetomidine as an adjuvant to neurosurgical case management.

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“…Cerebral blood vessels are reported to contract in response to norepinephrine (NE) via stimulation of postjunctional ␣ 1 -and/or ␣ 2 -adrenergic receptors (AR) (3,32). ␣ 2 -AR, which also may be prejunctional, have been shown to play an important role in cerebrovascular reactivity in several species (3,4,10,11,27,33,35,36,40,42). However, no unified role for cerebrovascular ␣ 2 -AR has been shown to exist throughout all species (18).…”

mentioning

confidence: 99%

Pre- and postjunctional α₂-adrenergic receptors in fetal and adult ovine cerebral arteries

Bishai

Penninga

Nijland

et al. 2002

American Journal of Physiology-Regulatory, Integrative and Comp

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In ovine cerebral arteries, adrenergic-mediated vasoconstrictor responses differ significantly with developmental age. We tested the hypothesis that, in part, these differences are a consequence of altered alpha(2)-adrenergic receptor (alpha(2)-AR) density and/or affinity. In fetal (approximately 140 days) and adult sheep, we measured alpha(2)-AR density and affinity with the antagonist [(3)H]idazoxan in main branch cerebral arteries and other vessels. We also quantified contractile responses in middle cerebral artery (MCA) to norepinephrine (NE) or phenylephrine in the presence of the alpha(2)-AR antagonists yohimbine and idazoxan and contractile responses to the alpha(2)-AR agonists clonidine and UK-14304. In fetal and adult cerebral artery homogenates, alpha(2)-AR density was 201 +/- 18 and 52 +/- 6 fmol/mg protein, respectively (P < 0.01); however, antagonist affinity values did not differ. In fetal, but not adult, MCA, 10(-7) M yohimbine significantly decreased the pD(2) for NE-induced tension in the presence of 3 x 10(-5) M cocaine, 10(-5) M deoxycorticosterone, and 10(-6) M tetrodotoxin. In fetal, but not adult, MCA, UK-14304 induced a significant decrease in pD(2) for the phenylephrine dose-response relation. In addition, stimulation-evoked fractional NE release was significantly greater in fetal than in adult cerebral arteries. In the presence of 10(-6) M idazoxan to block alpha(2)-AR-mediated inhibition of prejunctional NE release, the fractional NE release was significantly increased in both age groups. We conclude that in fetal and adult ovine cerebral arteries, alpha(2)-AR appear to be chiefly prejunctional. Nonetheless, the fetal cerebral arteries appear to have a significant component of postjunctional alpha(2)-AR.

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Postjunctional Alpha(2)-Adrenoceptors in Pial Arteries of Anesthetized Newborn Pigs

Cited by 34 publications

References 17 publications

Microvascular effects of atrial natriuretic factor: interaction with alpha 1- and alpha 2-adrenoceptors.

Microvascular effects of atrial natriuretic factor: interaction with alpha 1- and alpha 2-adrenoceptors.

Dexmedetomidine for Neurological Surgery

Pre- and postjunctional α₂-adrenergic receptors in fetal and adult ovine cerebral arteries

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Postjunctional Alpha(2)-Adrenoceptors in Pial Arteries of Anesthetized Newborn Pigs

Cited by 34 publications

References 17 publications

Microvascular effects of atrial natriuretic factor: interaction with alpha 1- and alpha 2-adrenoceptors.

Microvascular effects of atrial natriuretic factor: interaction with alpha 1- and alpha 2-adrenoceptors.

Dexmedetomidine for Neurological Surgery

Pre- and postjunctional α2-adrenergic receptors in fetal and adult ovine cerebral arteries

Contact Info

Product

Resources

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Pre- and postjunctional α₂-adrenergic receptors in fetal and adult ovine cerebral arteries