Key Points
- To assess how 4-aminopyridine alters isometric contractile force and electrical membrane potentials in isolated mammalian cardiac tissue.
- Mounted isolated papillary muscles from reserpinized rabbit hearts under isometric conditions (paced at 0.67 Hz, 37 °C) at 95% optimal length.
- Performed simultaneous electrophysiological and mechanical recordings during perfusion with 50 µM and 800 µM 4-aminopyridine, as well as one hour post-washout.
- Perfusion with 50 µM 4-aminopyridine increased peak isometric force by approximately 20% and prolonged action potential duration by 20% relative to control.
- A higher concentration of 800 µM expanded peak force by 60% and action potential duration by 70% over controls, with both electrical and mechanical potentiation persisting one hour after drug withdrawal.
Structured PICO
PPopulationIsolated papillary muscles from the heart of reserpinized rabbits
IIntervention4-aminopyridine (4-AP) at concentrations of 50 microM and 800 microM
CComparatorControl (baseline without 4-AP)
OOutcomeIsometric force and action potential durationsurrogate
4-aminopyridine prolongs the action potential and increases isometric force in rabbit papillary muscles, suggesting positive inotropic effects likely due to increased calcium uptake.