Figure 6.

Paired-pulse depression at ON synapses does not change with postnatal maturation of ETCs and PGCs, nor with maturation of adult-born GFP+ neurons. A, Paired-pulse AMPA responses evoked at varying ISIs at either −70 mV or +40 mV. Responses depressed strongly with a 50 ms ISI; this depression lessened with increasing ISI but was still evident at 5000 ms intervals. Values at each peak show the PPR calculated by dividing the peak amplitude of the second response by that of the first. B, Mean ± SEM. PPR values for all three cell types, over all maturation stages. A one-way ANOVA for responses at +40 mV revealed no significant differences between cell groups, whereas a two-way ANOVA for responses at −70 mV revealed significant differences between ISIs (p < 0.0001), but no significant differences between cell types, consistent with a presynaptic cause of PPR. C, Representative traces at −70 mV, 50 ms ISI for immature and mature stages in all three cell groups. Examples are normalized with respect to their initial peak; values at bottom are PPR. D, No significant correlations of PPR (−70 mV, 50 ms ISI) with maturation in any cell group. r and p report the results of nonparametric rank correlations. A, Adult. E, No significant group differences in PPR (−70 mV, 50 ms ISI) for any cell type. W1, Postnatal week 1; W4, postnatal week 4; 7–14, 45, and 90 refer to GFP+ cell groupings based on dpi.