Demonstration of slow channel activation in skeletal muscle of the dog.
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.
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*
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