Figure 6.

The Sr²⁺ dependence of asynchronous release in wild-type and Syt7 KO animals. A, Presynaptic divalent levels were measured in the presence of extracellular Ca²⁺ and extracellular Sr²⁺ using Mg-Green in wild-type and Syt7 KO animals as described in Materials and Methods. B, Synaptic currents were evoked by single stimuli in the presence of external Ca²⁺ and Sr²⁺ and peak EPSC amplitudes are shown as a function of time for representative cells. C, Example traces from cells shown in B in the presence of Ca²⁺ and Sr²⁺. D, Raster of quantal events shown during the application and washout of Sr²⁺ for example cells shown in B and C. E, Summary of delayed events evoked by single stimuli in the presence of Ca²⁺ and Sr²⁺ for wild-type (n = 7) and Syt7 KO mice (n = 7). F, Left, The frequency of quantal events in the presence of Ca²⁺ is shown as a function of time for wild-type (top graph, black) and Syt7 KO animals (top graph, red) in a semilogarithmic plot with logarithmic binning. A point-by-point ratio of the rate of events of wild-type to Syt7 KO animals is plotted in the lower graph. Right, Similar analysis but for events in the presence of Sr²⁺. Data are mean ± SEM. For some points error bars are occluded by markers.