ABSTRACT
Flavonoids from Thymus vulgaris L. have been studied in vitro for spasmolytic activity on the smooth muscles of the guinea-pig ileum and trachea and of the rat vas deferens. The flavones and thyme extracts inhibit responses to agonists which stimulate specific receptors (acetylcholine, histamine, L-noradrenaline) as well as to agents whose actions are not mediated via specific receptors (BaCl2). Cumulative dose-response curves point to a non-competitive antagonism. Inhibition of Ca2+ contractions on K+ depolarized smooth muscles suggest inhibition of availability of Ca2+ for muscle contraction. pD'2 values were determined to compare the potency of these components to each other and to standard drugs. Flavones induce relaxation of the carbachol contracted tracheal strip without stimulation of the beta 2-receptors, which were blocked by propranolol.
Subject(s)
Barium Compounds , Chlorides , Flavonoids/pharmacology , Parasympatholytics , Animals , Barium/pharmacology , Carbachol/pharmacology , Guinea Pigs , Histamine/pharmacology , Ileum/metabolism , In Vitro Techniques , Male , Muscle Contraction/drug effects , Muscle, Smooth/drug effects , Plants, Medicinal , Rats , Trachea/drug effects , Vas Deferens/drug effectsABSTRACT
Administration of 1,8-dihydroxyanthraquinone (DHA) markedly increases the permeability of guinea-pig colonic mucosa. In 1 h 25% of the administered dose of 99mTc-EDTA complex leaks through the mucosa. Orally administered loperamide blocks the 99mTc-EDTA transfer after DHA administration. Loperamide injected in situ in the ligated colon segment shows the same blocking properties of the transfer rate of the complex. These findings suggest that the opposing action on fluid transport of the laxative DHA and the antidiarrhoeal loperamide could be due to these drugs affecting the permeability of the colonic mucosa. The minimal dose of loperamide, able to restore normal permeability, was as low as 0.01 mg kg-1.
