Abstract
1. In vitro experiments in a microvascular myograph were designed to characterize postjunctional alpha-adrenoceptors of human subcutaneous resistance arteries (normalised internal diameter 143-313 microns). 2. Both the alpha 1-selective agonist phenylephrine in the presence of 0.3 microM yohimbine and the alpha 2-selective agonist B-HT 933 in the presence of 0.3 microM prazosin elicited prominent and concentration-dependent contractions. The maximum response to phenylephrine and B-HT 933 was not different from the response to high K physiological salt solution (125 mM K+), and the pD2 values (-log EC50) were 5.90 and 6.11, respectively. 3. In the presence of the alpha 2-selective antagonist yohimbine (0.3 microM), the alpha 1-selective antagonist prazosin competitively antagonised the responses to phenylephrine; the pA2 of prazosin for the receptor which mediated the response to phenylephrine was 8.41. 4. Blockade of either alpha 2-adrenoceptors with 0.1 microM yohimbine or alpha 1-adrenoceptors with 0.1 microM prazosin caused shifts to the right of the noradrenaline concentration-response curves and the shifts in pD2 were 0.69 and 0.61, respectively. The combination of the two antagonists at the above-mentioned concentrations caused a marked, parallel shift to the right of the noradrenaline concentration-response curve, the shift of the pD2 was 2.68. 5. These results suggest that activation of both alpha 1- and alpha 2-adrenoceptors produces contractions in human subcutaneous resistance arteries, and that responses to noradrenaline in these vessels are mediated by both alpha-adrenoceptor subtypes.
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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]
- Alabaster V., Davey M. Precapillary vessels: effects of the sympathetic nervous system and of catecholamines. J Cardiovasc Pharmacol. 1984;6 (Suppl 2):S365–S376. [PubMed] [Google Scholar]
- Busija D. W., Leffler C. W. Postjunctional alpha 2-adrenoceptors in pial arteries of anesthetized newborn pigs. Dev Pharmacol Ther. 1987;10(1):36–46. doi: 10.1159/000457726. [DOI] [PubMed] [Google Scholar]
- De Mey J., Vanhoutte P. M. Uneven distribution of postjunctional alpha 1-and alpha 2-like adrenoceptors in canine arterial and venous smooth muscle. Circ Res. 1981 Jun;48(6 Pt 1):875–884. doi: 10.1161/01.res.48.6.875. [DOI] [PubMed] [Google Scholar]
- Drew G. M. Pharmacological characterisation of the presynaptic alpha-adrenoceptor in the rat vas deferens. Eur J Pharmacol. 1977 Mar 21;42(2):123–130. doi: 10.1016/0014-2999(77)90351-x. [DOI] [PubMed] [Google Scholar]
- Drew G. M. What do antagonists tell us about alpha-adrenoceptors? Clin Sci (Lond) 1985;68 (Suppl 10):15s–19s. doi: 10.1042/cs068s015. [DOI] [PubMed] [Google Scholar]
- Ekenvall L., Lindblad L. E., Norbeck O., Etzell B. M. alpha-Adrenoceptors and cold-induced vasoconstriction in human finger skin. Am J Physiol. 1988 Nov;255(5 Pt 2):H1000–H1003. doi: 10.1152/ajpheart.1988.255.5.H1000. [DOI] [PubMed] [Google Scholar]
- Elliott H. L., Reid J. L. Evidence for postjunctional vascular alpha 2-adrenoceptors in peripheral vascular regulation in man. Clin Sci (Lond) 1983 Sep;65(3):237–241. doi: 10.1042/cs0650237. [DOI] [PubMed] [Google Scholar]
- Faber J. E. In situ analysis of alpha-adrenoceptors on arteriolar and venular smooth muscle in rat skeletal muscle microcirculation. Circ Res. 1988 Jan;62(1):37–50. doi: 10.1161/01.res.62.1.37. [DOI] [PubMed] [Google Scholar]
- Flavahan N. A., Cooke J. P., Shepherd J. T., Vanhoutte P. M. Human postjunctional alpha-1 and alpha-2 adrenoceptors: differential distribution in arteries of the limbs. J Pharmacol Exp Ther. 1987 May;241(2):361–365. [PubMed] [Google Scholar]
- Goldberg M. R., Robertson D. Evidence for the existence of vascular alpha 2-adrenergic receptors in humans. Hypertension. 1984 Jul-Aug;6(4):551–556. doi: 10.1161/01.hyp.6.4.551. [DOI] [PubMed] [Google Scholar]
- Jones S. B., Smith J. M., Jones A. W., Bylund D. B. Alpha-1 adrenergic receptor binding in aortas from rat and dog: comparison of [3H]prazosin and beta-iodo-[125I]-4-hydroxyphenyl-ethyl-aminomethyl-tetralone. J Pharmacol Exp Ther. 1987 Jun;241(3):875–881. [PubMed] [Google Scholar]
- Langer S. Z., Hicks P. E. Alpha-adrenoreceptor subtypes in blood vessels: physiology and pharmacology. J Cardiovasc Pharmacol. 1984;6 (Suppl 4):S547–S558. doi: 10.1097/00005344-198406004-00001. [DOI] [PubMed] [Google Scholar]
- Moulds R. J., Jauernig R. A. Mechanism of prazosin collapse. Lancet. 1977 Jan 22;1(8004):200–201. doi: 10.1016/s0140-6736(77)91808-6. [DOI] [PubMed] [Google Scholar]
- Mulvany M. J., Halpern W. Contractile properties of small arterial resistance vessels in spontaneously hypertensive and normotensive rats. Circ Res. 1977 Jul;41(1):19–26. doi: 10.1161/01.res.41.1.19. [DOI] [PubMed] [Google Scholar]
- Nielsen H., Thom S. M., Hughes A. D., Martin G. N., Mulvany M. J., Sever P. S. Postjunctional alpha 2-adrenoceptors mediate vasoconstriction in human subcutaneous resistance vessels. Br J Pharmacol. 1989 Jul;97(3):829–834. doi: 10.1111/j.1476-5381.1989.tb12022.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ruffolo R. R., Jr Interactions of agonists with peripheral alpha-adrenergic receptors. Fed Proc. 1984 Nov;43(14):2910–2916. [PubMed] [Google Scholar]
- Schümann H. J., Lues I. Postjunctional alpha-adrenoceptors in the isolated saphenous vein of the rabbit. Characterization and influence of angiotensin. Naunyn Schmiedebergs Arch Pharmacol. 1983 Aug;323(4):328–334. doi: 10.1007/BF00512471. [DOI] [PubMed] [Google Scholar]
- Sjöberg T., Steen S., Skärby T., Norgren L., Andersson K. E. Postjunctional alpha-adrenoceptors in human superficial epigastric arteries and veins. Pharmacol Toxicol. 1987 Jan;60(1):43–50. doi: 10.1111/j.1600-0773.1987.tb01717.x. [DOI] [PubMed] [Google Scholar]
- Skärby T. V., Andersson K. E., Edvinsson L. Pharmacological characterization of postjunctional alpha-adrenoceptors in isolated feline cerebral and peripheral arteries. Acta Physiol Scand. 1983 Jan;117(1):63–73. doi: 10.1111/j.1748-1716.1983.tb07179.x. [DOI] [PubMed] [Google Scholar]
- Starke K., Endo T., Taube H. D. Relative pre- and postsynaptic potencies of alpha-adrenoceptor agonists in the rabbit pulmonary artery. Naunyn Schmiedebergs Arch Pharmacol. 1975;291(1):55–78. doi: 10.1007/BF00510821. [DOI] [PubMed] [Google Scholar]
- Steen S., Sjöberg T., Skärby T. V., Norgren L., Andersson K. E. Postjunctional alpha 1- and alpha 2-adrenoceptors mediating contraction in isolated human groin arteries and veins. Acta Physiol Scand. 1984 Nov;122(3):323–329. doi: 10.1111/j.1748-1716.1984.tb07516.x. [DOI] [PubMed] [Google Scholar]
- Steen S., Skärby T. V., Norgren L., Andersson K. E. Pharmacological characterization of postjunctional alpha-adrenoceptors in isolated human omental arteries and veins. Acta Physiol Scand. 1984 Jan;120(1):109–116. doi: 10.1111/j.1748-1716.1984.tb07379.x. [DOI] [PubMed] [Google Scholar]
- Timmermans P. B., Kwa H. Y., van Zwieten P. A. Possible subdivision of postsynaptic alpha-adrenoceptors mediating pressor responses in the pithed rat. Naunyn Schmiedebergs Arch Pharmacol. 1979 Dec;310(2):189–193. doi: 10.1007/BF00500284. [DOI] [PubMed] [Google Scholar]
- Timmermans P. B., Van Zwieten P. A. Postsynaptic alpha 1- and alpha 2-adrenoceptors in the circulatory system of the pithed rat: selective stimulation of the alpha 2-type by B-HT 933. Eur J Pharmacol. 1980 May 2;63(2-3):199–202. doi: 10.1016/0014-2999(80)90446-x. [DOI] [PubMed] [Google Scholar]
