S-isopetasin, a sesquiterpene of Petasites formosanus, allosterically antagonized carbachol in isolated guinea pig atria

Wun Chang Ko, Sheng Hao Wang, Mei Chun Chen, Yun Lian Lin, Chieh Fu Chen

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

We investigated the antimuscarinic effect of S-isopetasin in isolated guinea pig atria to clarify whether it preferentially acts on muscarinic M2 or M3 receptors. The tension changes of isolated atria were isometrically recorded on a polygraph. S-Isopetasin at 50 and 100 μM significantly inhibited baselines of contractile tension and heart rate, but atropine at 1 μM enhanced both. S-Isopetasin (10-100 μM) did not significantly alter the concentration-negative inotropic response curves of carbachol (CCh) in left atria. S-Isopetasin (10-100 μM) allosterically antagonized negative inotropic and chronotropic responses induced by CCh in spontaneously beating right atria, based on the slopes of Schild plots significantly differing from unity. On the contrary, atropine (0.01-1 μM) competitively antagonized all the above responses to CCh. The pA2 values of S-isopetasin were significantly less than that of S-isopetasin in guinea pig trachealis, suggesting that S-isopetasin may preferentially act on tracheal muscarinic M3, but not cardiac muscarinic M2 receptors. However, atropine preferentially acts neither. This finding reveals that S-isopetasin may have benefit in the treatment of asthma.

Original languageEnglish
Pages (from-to)652-655
Number of pages4
JournalPlanta Medica
Volume68
Issue number7
DOIs
Publication statusPublished - 2002

ASJC Scopus subject areas

  • Plant Science
  • Drug Discovery
  • Organic Chemistry
  • Pharmacology

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