Figure 6.

A developmental increase in basal PPF ratio is associated with a decrease in the susceptibility to striatal LTD. (A) Basal PPF ratio plotted as a function of age (n = 171 cells). PPF ratio measured in P10–P15 group (n = 68) and P23–P27 group (n = 42) averaged 0.97 ± 0.02 and 1.29 ± 0.03, respectively (unpaired t test, P < 0.0001). There was no significant difference between the two age groups in average peak EPSC amplitude of the first pulse of the paired responses. The range of stimulus intensity used to evoke the response and series resistance of whole-cell patch-clamp recordings did not differ across age. (B) Summary of bar graph comparing changes induced by LTD induction in average peak EPSC amplitudes, PPF ratio, and CV values in P10–P19 group (n = 11) and P23–P27 group (n = 13). The difference in the magnitude of LTD and the increase in PPF after LTD induction between the two age groups was statistically significant (two-tailed, unpaired t test; ∗, P < 0.005; ∗∗, P < 0.05). There was no significant difference in the increase in CV after LTD induction between the two groups. PPF ratio and CV value after LTD induction in the P23–P27 group were 119.3 ± 3.8% and 139.9 ± 15.9% of control, respectively (P < 0.0005 and P < 0.05, respectively). Note that we failed to induce LTD in 4 out of 17 slices in the P23–P27 group and only the values from the 13 slices showing LTD are included in the graph. Basal PPF ratio in the neurons from the P10–P19 and P23–P27 groups in which LTD was examined averaged 1.017 ± 0.054 and 1.255 ± 0.056, respectively (two-tailed, unpaired test, P < 0.01).