Abstract
1 The effects of alpha-adrenoceptor antagonists on contractile responses to noradrenaline and methoxamine were examined in isolated saphenous vein strips of the dog. 2 Phentolamine, labetalol and thymoxamine antagonized responses to methoxamine to a greater extent than responses to noradrenaline. 3 Cocaine (3.0 x 10(-5) mol/l) increased the potency of noradrenaline by about eight fold, but had little or no effect on the potency of methoxamine. 4 In the presence of cocaine (3.0 x 10(-5) mol/l) the potency of the antagonists against noradrenaline was increased such that the pA2 values were then similar to those obtained against methoxamine. 5 It is concluded that the lower potency of phentolamine, labetalol and thymoxamine as antagonists of noradrenaline than of methoxamine is due to the presence of an avid saturable uptake1 process in the saphenous vein.
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Selected References
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- ARUNLAKSHANA O., SCHILD H. O. Some quantitative uses of drug antagonists. Br J Pharmacol Chemother. 1959 Mar;14(1):48–58. doi: 10.1111/j.1476-5381.1959.tb00928.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Apperley E., Humphrey P. P., Levy G. P. Receptors for 5-hydroxytryptamine and noradrenaline in rabbit isolated ear artery and aorta. Br J Pharmacol. 1976 Oct;58(2):211–221. doi: 10.1111/j.1476-5381.1976.tb10398.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Birmingham A. T., Szolcsányi J. Competitive blockade of adrenergic alpha-receptors and histamine receptors by thymoxamine. J Pharm Pharmacol. 1965 Jul;17(7):449–458. doi: 10.1111/j.2042-7158.1965.tb07701.x. [DOI] [PubMed] [Google Scholar]
- Furchgott R. F. The pharmacological differentiation of adrenergic receptors. Ann N Y Acad Sci. 1967 Feb 10;139(3):553–570. doi: 10.1111/j.1749-6632.1967.tb41229.x. [DOI] [PubMed] [Google Scholar]
- Gulati O. D., Parikh H., Umar M. S. Receptors for noradrenaline and histamine in the rabbit's posterior vena cava. Br J Pharmacol Chemother. 1968 Jan;32(1):87–95. doi: 10.1111/j.1476-5381.1968.tb00432.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Iversen L. L. The inhibition of noradrenaline uptake by drugs. Adv Drug Res. 1965;2:1–46. [PubMed] [Google Scholar]
- Janis R. A., Triggle D. J. On the question of subclassification of -adrenoceptors. J Pharm Pharmacol. 1973 Mar;25(3):263–264. doi: 10.1111/j.2042-7158.1973.tb10638.x. [DOI] [PubMed] [Google Scholar]
- Kalsner S., Nickerson M. Mechanism of cocaine potentiation of responses to amines. Br J Pharmacol. 1969 Mar;35(3):428–439. doi: 10.1111/j.1476-5381.1969.tb08284.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kalsner S. [Letter: The importance of adrenergic neuronal uptake in termination of action; another view. Response to i. s. de la lande]. Blood Vessels. 1975;12(5):316–322. doi: 10.1159/000158068. [DOI] [PubMed] [Google Scholar]
- Langer S. Z., Trendelenburg U. The effect of a saturable uptake mechanism on the slopes of dose-response curves for sympathomimetic amines and on the shifts of dose-response curves produced by a competitive antagonist. J Pharmacol Exp Ther. 1969 May;167(1):117–142. [PubMed] [Google Scholar]
- Patil P. N., Fudge K., Jacobowitz D. Steric aspects of adrenergic drugs. 18. -Adrenergic receptors of mammalian aorta. Eur J Pharmacol. 1972 Jul;19(1):79–87. doi: 10.1016/0014-2999(72)90079-9. [DOI] [PubMed] [Google Scholar]
- Sheys E. M., Green R. D. A quantitative study of alpha adrenergic receptors in the spleen and aorta of the rabbit. J Pharmacol Exp Ther. 1972 Feb;180(2):317–325. [PubMed] [Google Scholar]