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The β2-adrenoceptor antagonist CGP 20712 A unmasks β2-adrenoceptors activated by (−)-adrenaline in rat sinoatrial node

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Summary

The role of sinoatrial β1- and β2-adrenoceptors mediating positive chronotropic effects of (−)-adrenaline and (−)-noradrenaline was investigated in rat right atria. Concentration effect curves for (−)-adrenaline, but not for (−)-noradrenaline, became biphasic in the presence of the β1-adrenoceptors antagonist CGP 20712 A. The curves for (−)-adrenaline in the presence of 300 nmol/l CGP 20712 A (equivalent to 1,000 times its K B, K B=0.3 nmol/l for β1-adrenoceptors) comprise a high-sensitivity component that saturates at 1/4 of maximum effect, and a low sensitivity component. The high-sensitivity component is blocked by the β2-adrenoceptor-selective antagonist ICI 118,551. These results are consistent with an involvement in the rat of both β1-adrenoceptors (to a major extent) and β2-adrenoceptors [only at high (−)-adrenaline concentrations] in the positive chronotropic effects of (−)-adrenaline. (−)-Noradrenaline appears to activate mostly rat sinoatrial β1-adrenoceptors.

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Authors and Affiliations

  1. Department of Clinical Physiology, University of Düsseldorf, D-4000, Düsseldorf, Germany

    Alberto J. Kaumann

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  1. Alberto J. Kaumann
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Kaumann, A.J. The β2-adrenoceptor antagonist CGP 20712 A unmasks β2-adrenoceptors activated by (−)-adrenaline in rat sinoatrial node. Naunyn-Schmiedeberg's Arch. Pharmacol. 332, 406–409 (1986). https://doi.org/10.1007/BF00500096

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  • DOI: https://doi.org/10.1007/BF00500096

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