Alpha-1 and alpha-2 adrenoceptor: Response coupling in canine saphenous and femoral veins

Nicholas Flavahan, P. M. Vanhoutte

Research output: Contribution to journalArticle

Abstract

The aim of the present study was to analyze alpha-1 and alpha-2 adrenoceptor response coupling in isolated canine blood vessels. Rings of saphenous and femoral veins and of femoral arteries were suspended for isometric tension recording in modified Krebs-Ringer bicarbonate solution, gassed with 95% O2-5% CO2 and maintained at 37°C. Dissociation constants for the alpha-1 adrenergic agonists, phenylephrine and cirazoline, and the alpha-2 adrenergic agonist, UK 14,304, were determined by analysis of concentration-effect curves to the agonists under control conditions and after partial inactivation of alpha adrenoceptors by phenoxybenzamine. The dissociation constant of phenylephrine for alpha-1 adrenoceptors in saphenous veins was approximately 10-fold higher than that obtained for the agonist in femoral arteries or femoral veins. Similarly the dissociation constant for cirazoline in the saphenous vein was higher than that obtained in other alpha-1 adrenergic systems. Dissociation constants were used to determine alpha adrenoceptor occupancy-response relationships. The alpha-1 adrenergic responses evoked by intrinsic-efficacy agonists (cirazoline and phenylephrine) were associated with a very large receptor-reserve in the saphenous vein, but no, or only a limited receptor-reserve in the femoral vein. The dissociation constant for UK 14,304 in saphenous veins was significantly lower than that obtained for alpha-2 adrenergic stimulation by norepinephrine. There was no alpha-2 adrenoceptor reserve in the saphenous vein for these putative high intrinsic-efficacy agonists. The differences in receptor-reserve between alpha-1 adrenoceptors in canine saphenous and femoral veins and between alpha-1 and alpha-2 adrenoceptors in saphenous veins may help to explain the differential modulation of adrenergic responses in these blood vessels.

Original languageEnglish (US)
Pages (from-to)131-138
Number of pages8
JournalJournal of Pharmacology and Experimental Therapeutics
Volume238
Issue number1
StatePublished - 1986
Externally publishedYes

Fingerprint

Femoral Vein
Saphenous Vein
Adrenergic Receptors
Canidae
Adrenergic Agents
Phenylephrine
Femoral Artery
Blood Vessels
Adrenergic alpha-1 Receptor Agonists
Adrenergic alpha-2 Receptor Agonists
Phenoxybenzamine
Bicarbonates
Norepinephrine

ASJC Scopus subject areas

  • Pharmacology

Cite this

Alpha-1 and alpha-2 adrenoceptor : Response coupling in canine saphenous and femoral veins. / Flavahan, Nicholas; Vanhoutte, P. M.

In: Journal of Pharmacology and Experimental Therapeutics, Vol. 238, No. 1, 1986, p. 131-138.

Research output: Contribution to journalArticle

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