Antidiarrheal and antispasmodic activities of <i>Polygonum bistorta</i> rhizomes are mediated predominantly through K+ channels activation

Abstract

<p class="Abstract"><em>Polygonum bistorta</em> is a popular medicinal herb used to treat diarrhea. This study provides pharmacological basis to its folk use in diarrhea using <em>in vivo</em> and <em>in vitro</em> assays. Administration of<em> P. bistorta</em> rhizomes extract to mice offered protection against castor oil-induced diarrhea at 300-1,000 mg/kg and was found safe up to the dose of 5 g/kg. In isolated rabbit jejunum, the extract caused a dose-dependent relaxation of spontaneous and low K<sup>+</sup> (25 mM)-induced contractions with weak effect against high K<sup>+ </sup>(80 mM). In tissues pretreated with glibenclamide or tetraethylammonium chloride (TEA), the relaxant effect of the extract was markedly inhibited by TEA only. While verapamil showed complete relaxation of spontaneous, low K<sup>+</sup>, low K<sup>+</sup> with TEA and high K<sup>+</sup>-induced contractions. In guinea-pig ileum, mild atropine-sensitive effect was observed. This study indicates that <em>P. bistorta</em> possesses anti-diarrheal and antispasmodic activities mediated predominantly through K<sup>+</sup>-channels activation along with weak Ca<sup>++</sup> antagonist effect.</p><p> </p>