Oscillating contractions in protoplasmic strands of Physarum: effects of external Ca++-depletion and Ca++-antagonistic drugs on intrinsic contraction automaticity.
1. The minimal requirement of external Ca-concentration for continuance of contraction activity lies in the range of 10(-4) M. 2. As in mammalian smooth muscle, the Ca antagonistic drugs verapamil and D 600 (5.10(-4) M) suppress the minute-rhythms. The action of the drugs is inhibited by 5mM Ca, La or Mn. De novo generation of contraction automaticity is not inhibited by external Ca depletion or by Ca antagonists. 3. It is concluded that rhythmical Ca fluxes across the cortical plasmalemma are not a precondition for triggering continuance or de novo generation of contraction automaticity.
D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D003593:Cytoplasm / Q000502:physiology; D005711:Gallopamil / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D009068:Movement / Q000187:drug effects; D009235:Myxomycetes / Q000502:physiology*; D010804:Physarum / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology
D005711:Gallopamil; D008345:Manganese; D007811:Lanthanum; D014700:Verapamil; D002118:Calcium