Activity Dependent Potentiation

Activity dependent potentiation is the generic term that has been used to describe all forms of enhanced contractile response that can be attributed to prior activation: staircase, posttetanic potentiation and postactivation potentiation (PAP). The cellular mechanism that allows more force for a given activation is thought to be phosphorylation of the regulatory light chains of myosin. Phosphorylation of the light chains increases calcium sensitivity, which means there can be more force for a given level of submaximal calcium concentration. Maximal force is not enhanced, but the peak rate of force development is increased. Posttetanic potentiation, the electrical analogue of PAP, is an enhanced contractile response following an electrically induced tetanic contraction. Staircase is an enhanced contractile response during identical sequential submaximal activations, usually with single pulses of stimulation. However, staircase is also evident during sequential brief incompletely fused...