Short-term facilitation as a tool to know neuromodulator-induced change in Ca2+ movement in the nerve terminal

A theory was developed to show how we can predict the actions of neuromodulators on Ca2+ movement (yo: impulse-induced increase in Ca2+ concentration; c: basal Ca2+ level) in the nerve terminal from their effects on an impulse-evoked transmitter release (m: quantal content) and short-term facilitation (F) elicited by paired impulses, based on the simplest version of the residual Ca2+ hypothesis of facilitation. It was demonstrated from this theory that yo should be increased (decreased) when both m and F were increased (decreased) and that c should be increased (decreased) when m and F were increased (decreased) and decreased (increased), respectively. These ideas could interpret some published experimental results well.