Effects of ryanodine on the ionic currents and the calcium conductance in crab muscle fibers.
The effects of ryanodine, a neutral alkaloid, on crab muscle fibers were investigated under voltage clamp conditions using the double sucrose-gap technique. In the presence of ryanodine, contracture develops without any membrane depolarization and the Ca-conductance variables are shifted in a hyperpolarizing direction. As a result, the Ca channels are activated at the resting potential. During the action potential, the Ca channels appear to open faster and for a longer period of time. The K currents are also modified. These different effects may be interpreted by a common mechanism related to a change of the membrane electrical field induced by increased Ca activity in the cytoplasm.
D000200:Action Potentials / Q000187:drug effects; D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D003386:Brachyura / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D004594:Electrophysiology / Q000379:methods; D066298:In Vitro Techniques; D009132:Muscles / Q000187:drug effects*; D012433:Ryanodine / Q000494:pharmacology*; D013997:Time Factors
D000470:Alkaloids; D012433:Ryanodine; D002118:Calcium