Effect of Maturation on α-Adrenoceptor Activity in Newborn Piglet Mesentery

To characterize the mesenteric α1- and α2-adrenoceptor populations in newborn piglets, an extracorporeal circuit was established to control intestinal blood flow in 0- to 2-day old and 10- to 14-day old animals. In both groups, α-adrenoceptor activation was first documented by observing dose-depende...

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Bibliographic Details
Published in:The Journal of surgical research 1996-03, Vol.61 (2), p.330-338
Main Authors: Hoang, Thomas V., Choe, Ella U., Lippton, Howard L., Hyman, Albert L., Flint, Lewis M., Ferrara, John J.
Format: Article
Language:English
Subjects:
Age Factors
Animals
Animals, Newborn - physiology
Biological and medical sciences
Female
Fundamental and applied biological sciences. Psychology
Intestine. Mesentery
Male
Mesenteric Arteries - physiology
Prazosin - pharmacology
Receptors, Adrenergic, alpha - physiology
Swine
Vasoconstriction - drug effects
Vertebrates: digestive system
Yohimbine - pharmacology
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Summary:To characterize the mesenteric α1- and α2-adrenoceptor populations in newborn piglets, an extracorporeal circuit was established to control intestinal blood flow in 0- to 2-day old and 10- to 14-day old animals. In both groups, α-adrenoceptor activation was first documented by observing dose-dependent increases in mesenteric perfusion pressure after intramesenteric arterial injection of α-adrenoceptor agonists. In the 10-to 14-day old piglets, mesenteric vasoconstrictor responses to α1-adrenoceptor agonists (methoxamine and norepinephrine) and an α2-adrenoceptor agonist (BHT-933) were each blunted (P< 0.05, analysis of variance) by peripheral intravenous injections of prazosin (an α1-adrenoceptor antagonist) and yohimbine (an α2-adrenoceptor antagonist), respectively. The mesenteric vasoconstrictor responses to those agonists were not significantly attenuated by prazosin or yohimbine in 0- to 2-day old animals, nor were they blunted by YM-12617 (α1-adrenoceptor antagonist) or idazoxan (α2-adrenoceptor antagonist)—compounds that are structurally unrelated to prazosin and yohimbine, respectively. In addition, mesenteric vasoconstrictor responses to other known vasoconstrictor agents—angiotensin II, neuropeptide Y, and a thromboxane A2mimic (U-46619)—were not effected in either age group by prazosin or yohimbine, implying these agents act independently of α-adrenoceptor mechanisms. These data suggest that (1) there exists functional mesenteric α1- and α2-adrenoceptor-like activity in 10- to 14-day old piglets that, in 0- to 2-day old animals, is not specifically expressed; and (2) mesenteric α-adrenoceptor function becomes more selective as newborn piglets mature.
ISSN:0022-4804
1095-8673
DOI:10.1006/jsre.1996.0125