Ryanodine receptor open probability. Figure 15: RyR open probability modulation by concentration at the mouth. The pre-release diastolic [Ca2+]
is 918 μ M. The stimulation protocol used is a pulse of amplitude (-40 mv to 10 mv) and duration (50 ms). Phase A - As a result of excitation by the trigger current, [Ca2+]
initially increases rapidly with a small accompanying rise in RyR open probability followed by steeper increase to peak [Ca2+]
with a large increase in RyR open probability.; Phase B - RyR open probability increases to its maximum value at a declining rate reflecting a falling [Ca2+]
level and onset of Ca2+ induced self-inhibition; Phase C - Decreasing Ca2+
and continued Ca2+ induced self-inhibition, begins the channel recovery process; Phase D - Decreasing [Ca2+]
forces a strong RyR inactivation via the luminal sensor hence robustly closing the channel.