Figure 3

GABA synapses onto interneurons in stratum radiatum show a multiplicity higher than one already in the developing rats. (A₁) A typical recording at 0 mV from an interneuron in stratum radiatum from a P9 rat, upper trace shows GABA sIPSCs under control conditions and lower trace shows mIPSCs after wash-in of TTX. (A₂) TTX reduces the GABA IPSC amplitude by 5.4 ± 2.0 pA (P = 0.04, n = 6, two-tailed paired t-test). (A₃) TTX reduces GABA IPSC frequency by 4.3 ± 1.0 Hz (P = 0.0045, n = 6, one-tailed paired t-test). (B₁) A typical recording at 0 mV from an interneuron from a P43 rat, upper trace shows GABA sIPSCs under control conditions and lower trace shows mIPSCs after wash-in of TTX. (B₂) TTX reduces the GABA IPSC amplitude by 1.8 ± 0.7 pA (P = 0.02, n = 11, two-tailed paired t-test). (B₃) TTX reduces GABA IPSC frequency by 3.9 ± 0.7 (P < 0.001, n = 11, one-tailed paired t-test). (C) The average multiplicity was 1.7 ± 0.3 (P = 0.025, n = 6, one-tailed one-sample t-test with test value = 1) for the young age group (P7-16, open circles) and 2.0 ± 0.4 (P = 0.014, n = 11, one-tailed one-sample t-test with test value = 1) for the older rats (> P30, filled circles). Black filled circles show mean ± SEM and red open and filled circles show individual experiments. Asterisks denote the level of significance as follows: *: P < 0.05, **: P < 0.01, ***: P < 0.001.