Quantitative Analysis Linking Inner Hair Cell Voltage Changes and Postsynaptic Conductance Change: A Modelling Study

Figure 11

Row (a) illustrates the results from a disk shaped synaptic ribbon resembling a mammalian photoreceptor synapse and row (b) shows the simulations from an ellipsoid shaped synaptic ribbon resembling a mammalian auditory synapse while the third row (c) depicts the results from a sphere shaped ribbon with dimensions taken from those obtained from an amphibian papilla. For a list of numerical parameters see Table 1. The first column graphically displays the locations of all synaptic neurotransmitter vesicles in the model; blue marks the freely floating vesicles and green marks the ribbon tethered vesicles while red marks the vesicles that are free for release given their proximity to the membrane; the calcium channels are indicated with black dots. The second column plots together the presynaptic calcium ion influx (red) and the corresponding postsynaptic conductance of the opposite auditory nerve neurite (blue). The -axis indicates the variation in intensity of the 100 ms voltage pulses used to excite the synapse. The third column is a histogram of the inter-vesicle release time intervals (IVT) of all the vesicle releases. All histograms exhibit a peak at roughly 2.3 ms. In other words, when the synapse is fully driven by a step change in the intracellular voltage, a neurotransmitter filled vesicle will tend to be released at around 430 Hz.

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(b)

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