Pre- and postjunctional alpha 2-adrenergic receptors in fetal and adult ovine cerebral arteries

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2002-06, Vol.282 (6), p.1654-R1662
• Main Authors: Bishai, John M, Penninga, Luit, Nijland, Roel, Meulenaar, Rogier, Gheorghe, Ciprian P, Zhao, Yu, Buchholz, John N, Zhang, Lubo, Longo, Lawrence D
• Format: Article
• Language: English
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00475.2001

Center for Perinatal Biology, Departments of Physiology, Pharmacology, and Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, California 92350 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 2 -adrenergic receptor ( 2 -AR) density and/or affinity. In fetal (~140 days) and adult sheep, we measured 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 2 -AR antagonists yohimbine and idazoxan and contractile responses to the 2 -AR agonists clonidine and UK-14304. In fetal and adult cerebral artery homogenates, 2 -AR density was 201 ±   18 and 52 ± 6 fmol/mg protein, respectively ( P