Key Points
- To determine how stimulation frequency and rest intervals influence the positive and negative inotropic responses of rat atrial muscle exposed to caffeine.
- Exposed isolated rat atrial muscle to caffeine concentrations ranging from 1.0 to 10 mM during electrical stimulation at 0.1, 0.5, 2.0, and 3.0 Hz.
- Assessed postrest potentiation following pauses of 2 to 20 seconds after 0.5 or 3.0 Hz stimulation in the presence and absence of 2.0 mM caffeine.
- At 0.5 and 2.0 Hz stimulation, caffeine (1, 5, or 10 mM) produced a transient positive followed by a negative inotropic response accompanied by incomplete relaxation and contracture.
- At 0.1 Hz stimulation, caffeine produced exclusively negative inotropic effects, with greater inhibition observed at 1 mM than at 5 mM caffeine.
- Presence of 2.0 mM caffeine severely attenuated postrest potentiation following 2- to 20-second pauses, while steady-state contraction amplitude remained unchanged between 0.5 and 3.0 Hz.
Structured PICO
PPopulationRat atrial muscle
IInterventionCaffeine (1.0-10 mM)
CComparatorAbsence of caffeine
OOutcomeInotropic response (force-frequency and postrest characteristics)surrogate
Caffeine exerts frequency-dependent inotropic effects on rat atrial muscle, consistent with inducing calcium leak from the sarcoplasmic reticulum.