Figure 7.

The presynaptic Fmr1 deletion phenotype can be mimicked with a decrease in release probability in presynaptic WT pairs. A, Left, Example average traces before and after 4 μm CdCl₂. Right, We obtained the relationship between CdCl₂ (Cd⁺²) concentration and blockade of uEPSC1. Data were fitted to a sigmoid curve. Dashed lines mark the [Cd⁺²] (2.6 μm) that corresponds to the average fractional decrease of uEPSC1 amplitude found for presynaptic Fmr1 deletion (0.40). B, Example average traces obtained from a WT/WT pair in the presence of 2.6 μm CdCl₂ before and after kynurenate (Kyn; 250 μm) application. C, Average blockade by kynurenate with 2.6 μm CdCl₂ closely matched the blockade for presynaptic KO pairs. D, No change in short-term plasticity with Cd²⁺ application. WT/WT and KO/WT data in C and D are replotted from Figure 5. *p < 0.05. Calibrations: 20 pA, 2 ms.