Interaction of XXXX , @entity1855 , and @entity3988 on hamster diaphragm muscle force in vitro.

@entity3988 @entity1855 @entity2544 @entity460
The effect of the @entity460 channel blocker @entity1855 (5 microM) or @entity3988 (5 microM) on force production and resting membrane potential (Em) was studied in the hamster diaphragm muscle. The @entity460 channel blockers decreased force at high frequencies of stimulation and decreased Em by 3 +/- 1 mV. The interaction of @entity2544 and the @entity460 channel blockers was also studied. When given simultaneously, the @entity460 channel blockers prevented the increase in force at high frequencies with @entity2544 at 1 mM and at all frequencies with @entity2544 at 0.55 mM. There was no change in Em when @entity2544 and @entity460 channel blockers were given together. Similar results were obtained by removing external @entity460 . The decrease in force produced by @entity1855 was not reversed by subsequent addition of @entity2544 . @entity2544 did reverse the decrease in force produced by @entity3988 . @entity1855 reversed the increase in force at high frequencies produced by @entity2544 . @entity3988 reversed the force increase at low frequencies as well. These studies suggest that extracellular @entity460 is important in skeletal muscle contractility especially at high frequencies. Extracellular @entity460 is also important for the potentiation of force and the hyperpolarization of the Em produced by @entity2544 . The mechanism by which extracellular @entity460 contributes to these actions of @entity2544 is not known.
