Figure 1. Effects of Cd²⁺ on release and MPD at the BC-GC synapse.

A, train of presynaptic action potentials evoked by brief current pulses (top trace) and corresponding average IPSCs (bottom traces) in control, in the presence of 10 μm Cd²⁺ and after wash. Lowermost traces show the first and the last IPSC of the train in control and Cd²⁺ on an expanded time scale, superimposed after normalization of IPSC₁ to the same peak amplitude. Average IPSCs were obtained from 50 individual sweeps. B, plot of peak amplitude of first IPSC (IPSC₁; single traces) against time during Cd²⁺ application. Same pair as in A. C, mean ratio of IPSC_n/IPSC₁, plotted against the number within the train (n). ○, data in control; •, data in 10 μm Cd²⁺; □, data after wash (all normalized to IPSC₁ in control). ▪, data in 10 μm Cd²⁺ (normalized to IPSC₁ in Cd²⁺). The stimulation frequency during the train was 50 Hz in all experiments. Curves represent exponential fits to control data points (continuous; τ= 25 ms, offset 0.34) and data points in Cd²⁺ (dashed; τ= 20 ms, offset 0.29). Data from 7 (control), 7 (10 μm Cd²⁺) and 6 pairs (wash).