[Functioning of the electromechanical connection in the course of the contracture contraction].
The effects of calcium release blocker dantrolene was tested on electrically evoked twitches and on contractures induced by potassium depolarization, by acetylcholine or caffeine. It was shown that the first: developmental, stage of potassium or acetylcholine contracture is inhibited by dantrolene and is not influenced by calcium free medium, therefore we may interpret it as based on a "voltage-dependent Ca release" (VDCR) mechanism of activation, whereas depolarization directly opens the rhyanodin receptor calcium channels. On the contrary, the next stage: the long-lasting plateau of contracture, is directly dependent on external Ca2+ and inhibited by dantrolene, and therefore can be described as "calcium induced Ca-release" (CICR) activation mechanism. In this case stored calcium is also released by rhyanodine receptors, although by means of entering the extracellular Ca2+. Finally, the last stage of low amplitude is not influenced by dantrolene nor by calcium-free medium. Therefore the activation of contraction on this stage is not based on the Ca2+ release through the rhyanodin receptor calcium channels.
Nasledov
G A
GA
I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Acad. Sci., 194223, St. Petersburg, pr. M. Toreza, 44, Russia.
Katina
I E
IE
Kobzeva
M A
MA
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001696:Biomechanical Phenomena; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003620:Dantrolene / Q000494:pharmacology; D066298:In Vitro Techniques; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D011896:Rana temporaria; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D002121:Calcium Channel Blockers; D019837:Ryanodine Receptor Calcium Release Channel; D014662:Vasoconstrictor Agents; D003620:Dantrolene; D000109:Acetylcholine; D011188:Potassium