title: Effects of midodrine, ST 1059, methoxamine and glycine on spontaneously beating guinea-pig atria.
abstract: The chronotropic effects of midodrine, glycine (10(-8) to 3.10(-3) M), ST1059 and methoxamine (10(-8) to 10(-3) M) were investigated in the spontaneously beating guinea-pig right atrial preparation. Midodrine and glycine produced a slight, but significant rise in atrial rate over a wide concentration range. The midodrine-induced rise in atrial rate was not influenced by the beta-adrenergic receptor blocking drug propranolol (10(-6) M). The histamine (H2)-receptor blocking drug metiamide (3.10(-5) M) abolished the positive chronotropic actions of both midodrine and glycine. No positive chronotropic effect was seen after the administration of ST 1059 or methoxamine. A decrease in atrial rate was elicited by high concentrations (above 10(-4) to 10(-3) M) of the sympathomimetic agents midodrine, ST 1059, and methoxamine, but not by the amino acid glycine.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D004983:Ethanolamines / Q000494:pharmacology*; D005260:Female; D005998:Glycine / Q000494:pharmacology*; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects*; D006873:Hydroquinones / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008729:Methoxamine / Q000494:pharmacology*; D008785:Metiamide / Q000494:pharmacology; D008879:Midodrine / Q000494:pharmacology* / Q000031:analogs & derivatives; D011433:Propranolol / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D004983:Ethanolamines; D006873:Hydroquinones; C006146:ST 1059; D008785:Metiamide; D008879:Midodrine; D011433:Propranolol; D008729:Methoxamine; D005998:Glycine