Figure 4.
Unaltered voltage-gated Ca2+ currents and similar RRP size in Cplx1−/− calyx terminals. A, SV exocytosis triggered by presynaptic Ca2+ influx and recorded by capacitance measurements. Representative presynaptic ICa(V) and the corresponding changes in membrane capacitance (ΔCm) evoked by step depolarizations of 1, 2, 3, 5, 9, 17, 33, and 50 ms duration from Vh = −80 to 0 mV were recorded with 0.5 mm EGTA in the pipette solution in a Cplx1+/+ (A1) and a Cplx1−/− (A2) terminal. B,C, Scatter plots of peak amplitudes of ICa(V) (B) and corresponding maximum ΔCm values (obtained from 50 ms step depolarizations) as a function of postnatal age. Solid lines represent linear regressions. Both ICa(V) as well as exocytosis increased similarly in Cplx1+/+ (gray circles) and Cplx1−/− (red circles) terminals with maturation. Number of terminals tested as indicated. D, Average ΔCm values plotted as a function of step depolarization length for Cplx1+/+ (black) and Cplx1−/− (red) terminals. Data were grouped into two developmental stages: P8–P10 (open symbols) and P16–P20 (filled symbols). ΔCm values were similar for wt and Cplx1−/− terminals throughout development. E, F, Averaged peak amplitudes of ICa(V) (E) and ΔCm values (50 ms step depolarizations; F) for Cplx1+/+ (black) and Cplx1−/− (red) terminals. Number of terminals tested as indicated.