The interaction between facilitation and depression of two release mechanisms in a single synapse

The synapse from the lateral pyloric (LP) to the pyloric dilator (PD) neuron in the stomatogastric nervous system of the crab Cancer borealis has both a graded and a spike-mediated component. These two components have opposite short-term dynamics: the spike-mediated component is usually facilitating, while the graded component is depressing. We built a model of these two synaptic components and their interactions, based on the concept of quantal release evoked by calcium influx. This model is able to accurately predict the postsynaptic response of the PD neuron to any temporally patterned presynaptic LP neuron activity.