Characterization of alpha-adrenoceptor activity in the preterm piglet mesentery.
To characterize neonatal mesenteric alpha-adrenoceptor populations, an extracorporeal perfusion circuit was established to control intestinal blood flow in prematurely delivered (by cesarean section at 90% of gestational age) piglets. Activation of alpha 1-adrenoceptors was documented by observing dose-dependent increases in mesenteric perfusion pressure after intramesenteric arterial injection of methoxamine; alpha 2-adrenoceptor activity was confirmed by finding similar increases in mesenteric perfusion pressure after intramesenteric arterial injections of BHT 933. Peripheral intravenous injections of WB 4101 (a competitive alpha 1A-adrenoceptor antagonist), but not clorethylclonidine (CEC, an alpha 1B-adrenoceptor antagonist), significantly blunted (P < .05, ANOVA) the mesenteric vasoconstrictor responses to methoxamine. The mesenteric vasoconstrictor response to BHT 933 (an alpha 2-adrenoceptor agonist) also was blunted by WB 4101, but not by CEC. These data suggest that alpha 1A- and alpha 2-adrenoceptors can be activated in the small intestinal mesentery of piglets well before they reach full-term maturation, although receptor specificity has not been fully established.
Hoang
T V
TV
Department of Surgery, Tulane University School of Medicine, New Orleans, LA 70112, USA.
Choe
E U
EU
Burgess
R S
RS
Cork
R C
RC
Flint
L M
LM
Ferrara
J J
JJ
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001381:Azepines / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D005260:Female; D005325:Fetal Organ Maturity / Q000502:physiology; D008638:Mesenteric Arteries / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D008729:Methoxamine / Q000494:pharmacology; D010477:Perfusion; D011247:Pregnancy; D011312:Pressure; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism* / Q000502:physiology; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D001381:Azepines; D004146:Dioxanes; D011942:Receptors, Adrenergic, alpha; C015603:azepexole; C010654:(2-(2',6'-dimethoxy)phenoxyethylamino)methylbenzo-1,4-dioxane; D008729:Methoxamine