The surmountable effect of FSCPX, an irreversible A1 adenosine receptor antagonist, on the negative inotropic action of A1 adenosine receptor full agonists in isolated guinea pig left atria

Rudolf Gesztelyi, Zsuzsanna Kiss, Zita Wachal, Bela Juhasz, Mariann Bombicz, Evelin Csepanyi, Krisztian Pak, Judit Zsuga, Csaba Papp, Zoltan Galajda, Klara Branzaniuc, Robert Porszasz, Andras Jozsef Szentmiklosi, Arpad Tosaki

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A1 adenosine receptors (A1 receptors) are widely expressed in mammalian tissues; therefore attaining proper tissue selectivity is a cornerstone of drug development. The fact that partial agonists chiefly act on tissues with great receptor reserve can be exploited to achieve an appropriate degree of tissue selectivity. To the best of our knowledge, the A1 receptor reserve has not been yet quantified for the atrial contractility. A1 receptor reserve was determined for the direct negative inotropic effect of three A1 receptor full agonists (NECA, CPA and CHA) in isolated, paced guinea pig left atria, with the use of FSCPX, an irreversible A1 receptor antagonist. FSCPX caused an apparently pure dextral displacement of the concentration-response curves of A1 receptor agonists. Accordingly, the atrial A1 receptor function converging to inotropy showed a considerably great, approximately 80-92 % of receptor reserve for a near maximal (about 91-96 %) effect, which is greater than historical atrial A1 receptor reserve data for any effects other than inotropy. Consequently, the guinea pig atrial contractility is very sensitive to A1 receptor stimulation. Thus, it is worthwhile considering that even partial A1 receptor agonists, given in any indication, might decrease the atrial contractile force, as an undesirable side effect, in humans.

Original languageEnglish
Pages (from-to)293-305
Number of pages13
JournalArchives of Pharmacal Research
Issue number3
Publication statusPublished - Mar 1 2013



  • A adenosine receptor
  • Atrium
  • Guinea pig
  • Inotropy
  • Receptor reserve

ASJC Scopus subject areas

  • Molecular Medicine
  • Drug Discovery
  • Organic Chemistry

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