title: Demonstration of slow channel activation in skeletal muscle of the dog.
abstract: The effects of verapamil, MnCl2, CaCl2 and tetrodotoxin on the contracture induced by KCl infusion were studied on the isolated, blood-perfused canine diaphragm preparation. Continuous intra-arterial infusion of KCl (30-100 mg/min) produced a biphasic contracture; initially a fast and large contracture was induced which soon declined and was replaced by a second smaller contracture which was sustained throughout the KCl infusion. Verapamil (3 micrograms-10 mg, i.a.) and MnCl2 (0.1-10 mg, i.a.) produced a dose-dependent relaxation in the sustained contracture. Intra-arterial injection of CaCl2 produced a dose-dependent contractile response which was inhibited by treatment with verapamil and MnCl2. On the other hand tetrodotoxin, even in high doses, did not show a significant inhibitory effect on the sustained potassium-induced contracture. Therefore, the present results indicate that the slow calcium channel of skeletal muscle of the dog was activated with depolarization induced by potassium infusion.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002122:Calcium Chloride / Q000494:pharmacology; D002712:Chlorides; D004285:Dogs; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D008345:Manganese / Q000494:pharmacology; D017895:Manganese Compounds; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D002712:Chlorides; D007473:Ion Channels; D017895:Manganese Compounds; D008345:Manganese; D013779:Tetrodotoxin; D011189:Potassium Chloride; D014700:Verapamil; D002122:Calcium Chloride; C025340:manganese chloride; D002118:Calcium