Effect of Ca2+ on presynaptic facilitation
We investigated and modeled the effect of Ca2+ on presynaptic facilitation. Facilitation of transmitter release from a presynaptic terminal is believed to arise from the local increase of Ca2+ concentration. We measured and simulated the effect of Ca2+ on facilitation at the lobster neuromuscular synapse. Facilitation was measured using quantal analysis of postsynaptic potentials recorded focally during trains of stimuli. We found a facilitation component, which was not affected by Ca2+ concentration. Transmitter release was simulated using a model of two pools of presynaptic vesicles available for release. The simulation reproduced quantitatively Ca2+-dependent and Ca2+-independent components of facilitation.
intracellular ca2+ synaptic transmission neuromuscular junction releasable pool of synaptic vesicles neurosecretion