title: [Amplitude fluctuations in the contractile responses of small fragments of rat papillary muscle].
abstract: Contractile responses of small rat papillary muscle segments (length = 0.25 mm) superfused in a normal Tyrode's solution (t = 35 degrees C) and stimulated at a frequency of 0.16 Hz have been measured, using an original technique. The amplitude of contractile responses was found to fluctuate with the variation of 3.0 +/- 0.4 mu, though the contraction amplitude of the entire muscle remained constant from beat to beat. After the addition of caffeine (6 mM) the variation of contractile responses decreased up to 0.83--0.03 mu, demonstrating a crucial role of sarcoplasmic reticulum in the phenomenon. It is believed that contractility inhibition during calcium overload may be caused by the same reason.
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors; D004558:Electric Stimulation / Q000295:instrumentation; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects / Q000502:physiology*; D051381:Rats
chemical_list: D002110:Caffeine; D002118:Calcium
vernacular_title: Fluktuatsii amplitud sokratitel'nykh otvetov malykh fragmentov papilliarnoĭ myshtsy krysy.