Modelling Vesicular Release at Hippocampal Synapses
Figure 7
Response to a 200 ms at 50 Hz rate stimulus protocol administered to a model CA3-CA1 synapse with seven docked vesicles.
In (A) and (B) a synapse with low intrinsic release probability of pr = 0.2, in (C and D) a synapse with a release probability of pr = 0.6 and in (E and F) a high release probability synapse (pr = 0.9) is shown. In the high pr synapse, depletion quickly overwhelms release. Comparing A to B, C to D and E to F, the base level asynchronous release was higher in the synapse with refractoriness (black) whereas the synapse without refractoriness (grey) had higher peak release rates. This is because the refractoriness inhibits immediate release (less that 6 ms interval) from the synchronous pathway and therefore allows the asynchronous release pathway to contribute more to the release. The rates of facilitation and depression were also characteristically different for these synapses.