Dissociation of calcium- and barium-induced contractions of the rat duodenum smooth muscle.
The contractile responses elicited by calcium (Ca) and barium (Ba) upon the isolated rat duodenum immersed in a Ca-free Tyrode solution are not nervously mediated and are differently affected by epinephrine (E), cocaine (C) and verapamil (V). E antagonizes Ca but not Ba while C inhibits only Ba. The antagonism of V is greater towards Ba than Ca. The different influence of the drugs disappear in the excess potassium-depolarized duodenum. Thus, C and V block equally Ca and Ba, while E is only slightly effective against the two cations.
D000818:Animals; D001464:Barium / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D003042:Cocaine / Q000494:pharmacology; D004386:Duodenum / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
D001464:Barium; D014700:Verapamil; D003042:Cocaine; D011188:Potassium; D002118:Calcium; D004837:Epinephrine