Evidence that the population of postjunctional-adrenoceptors mediating contraction of smooth muscle in the rabbit isolated ear vein is predominantly α2

Daly, C.J. , McGrath, J.C. and Wilson, V.G. (1988) Evidence that the population of postjunctional-adrenoceptors mediating contraction of smooth muscle in the rabbit isolated ear vein is predominantly α2. British Journal of Pharmacology, 94(4), pp. 1085-1090. (doi: 10.1111/j.1476-5381.1988.tb11626.x)

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Abstract

1: Noradrenaline (NA), phenylephrine and UK-14304 elicited concentration-dependent contractions of the rabbit isolated ear vein of similar maximal magnitude. The rank order of potency, UK-14304 > noradrenaline > phenylephrine, is consistent with that of an effect mediated through an α2-subtype.<p></p> 2: The potent and highly selective α1-adrenoceptor antagonists prazosin and YM-12617, at concentrations as high as 1 μm, produced less than a 4 fold rightward displacement of the NA concentration-response curve.<p></p> 3: The selective α2-adrenoceptor antagonists rauwolscine, Wy-26703 and CH-38083 antagonized responses to noradrenaline in a competitive manner. For all three antagonists, the pA2 values were consistent with an effect at α2-adrenoceptors. However, 0.1 μm YM-12617 increased the potency of rauwolscine 2 fold indicating the presence of a small population of postjunctional α1-adrenoceptors.<p></p> 4: The relative antagonist potency of the yohimbine diastereoisomers rauwolscine and corynanthine against noradrenaline (rauwolscine 30 fold > corynanthine) is also consistent with an effect at α2-adrenoceptors.<p></p> 5: Contractions elicited by noradrenaline in the rabbit isolated ear vein appear to be mediated predominantly by postjunctional α2-adrenoceptors.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:McGrath, Professor John and Daly, Dr Craig
Authors: Daly, C.J., McGrath, J.C., and Wilson, V.G.
College/School:College of Medical Veterinary and Life Sciences > School of Life Sciences
Journal Name:British Journal of Pharmacology
Publisher:John Wiley & Sons, Inc.
ISSN:0007-1188
ISSN (Online):1476-5381

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