Impact of probability of vesicle release on neuronal firing

One well established phenomenon in the CNS is every action potentials does not trigger neurotransmitter release from a single presynaptic terminal. Observations in hippocampal slice and from two photon calcium imaging in vivo suggest that probability of release at a single excitatory synapse is significantly less than .5. We wanted to examine the impact of the probability of release and variance in probability of release on synaptic input to pyramidal neurons. To accomplish this we modeled inputs from probabilistically speaking upstream neurons, varying the mean and variance of the probability of vesicle release for the same upstream spiking pattern and distribution of synapses and examined the impact on spiking in a single downstream layer 2/3 pyramidal neuron. We used NEURON to model this biophysically realistic downstream pyramidal cell.