Using ephaptic coupling to estimate the synaptic cleft resistivity of the calyx of Held synapse
Fig 6
Potential impact of the cleft potential on presynaptic calcium currents.
(A) Simulation of the impact of a slow and a fast AP (top; FWHM: left 1.0, right 0.2 ms) on the cleft potential (second row), the transmembrane potential sensed by the calcium channels in the cleft (third row) and the presynaptic calcium current (bottom) at three leak resistances (1/gcl: 0 MΩ, 1 MΩ and 5 MΩ). Scale bar: 200 mV, 40 mV, 50 mV, 1 nA. (B) Relation between peak calcium currents and leak resistance for the two APs. Driving force slightly increases (not illustrated). (C) The change in delay between the calcium peak current and the AP for the two APs (solid line). The dashed line shows the delay after correcting for the decrease in the calcium current shown in B. Calcium conductance density was adjusted to 0.2 nS μm-2 and 2.8 nS μm-2 for the slow and fast AP, respectively, in order to elicit a 2 nA-current at 0 MΩ cleft leak resistance. The apposition area was 1000 μm2. Other conductances were set to 0 nS.