W. SuvitayavatS. TunlertS. S. ThirawarapanC. KitpatiN. BunyapraphatsaraMahidol University2018-06-212018-06-212005-08-02Phytomedicine. Vol.12, No.8 (2005), 561-569094471132-s2.0-21744439270https://repository.li.mahidol.ac.th/handle/20.500.14594/16307The effect of the Thai popular medicine Ya-hom on cardiovascular function was studied in isolated rat aortic ring and atrium by comparison with norepinephrine (NE). Water extraction of Ya-hom at concentrations of 0.83, 1.67, 8.33 and 16.67 mg/ml stimulated aortic ring contraction dose-dependently. The maximum contraction, at 16.67 mg/ml, was about 14% that of NE. This stimulatory effect of Ya-hom was inhibited partially by phentolamine, which indicated that the effect of Ya-hom was partially dependent on the α receptor, similar to NE. Administration of Ya-hom with NR decreased the force of aortic ring contraction as compared to the effect of NE alone, indicating that Ya-hom may have a partial α-agonist activity. Ya-hom at concentrations of 1.67, 8.33 and 16.67 mg/ml showed a dose-dependent, positive inotropic and negative chronotropic effects. Ya-hom increased the force of isolated atrial contraction with a slow onset and prolonged action. In contrast to norephinephrine, which acted on β1receptor, causing positive inotropic and chronotropic effects, propranolol did not alter the effect of Ya-hom on the atrial contraction. This shows that the action of Ya-hom on atrial contraction does not involve β receptor. This study demonstrated that the selected Ya-hom preparation increased vascular smooth muscle contraction, and increased the force but decreased the rate of atrial contraction. © 2005 Elsevier GmbH. All rights reserved.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyMedicinePharmacology, Toxicology and PharmaceuticsArticleSCOPUS10.1016/j.phymed.2004.03.014