Article Figures & Data
Figures
- Figure 1.
IPSCs and EPSCs recorded in layer IV pyramidal cells in response to thalamic stimulation. A, Left, A thalamocortical brain slice preparation (cytochrome c oxidase staining). Scale bar, 1 mm. The black pointer indicates a typical position of stimulation. A barrel is indicated by a dotted circle. Recordings were made from neurons within a barrel. VB, Ventrobasal nucleus of the thalamus; IC, internal capsule. Right, The scheme of the thalamocortical circuit. B1, Synaptic currents evoked by thalamic stimulation were recorded from layer IV pyramidal cells in wt and tg mice (P21–P30). EPSCs were recorded at a holding potential of −60 mV (top traces). When the holding potential was 0 mV, IPSCs became prominent (bottom traces). B2, The outward currents at a holding potential of 0 mV were blocked by picrotoxin (50 μm) (left) and also abolished by CNQX (10 μm) (right). B3, The IPSC and EPSC traces are superimposed in an expanded timescale (the same data used in B1 for wt). The mean delay between the onset EPSC and IPSC was 1.3 ± 0.08 ms (n = 12) for wt and 1.4 ± 0.15 ms (n = 11) for tg mice. C, The relationship between the excitatory and inhibitory conductances. Each point represents data from a single neuron.
- Figure 2.
Impaired IPSCs of layer IV pyramidal cells in tg mice (P21–P30). IPSCs and EPSCs were evoked by local stimulation in layer IV pyramidal cells in wt and tg mice at P21–P30. A, IPSCs were recorded in the presence of CNQX (10 μm) and APV (100 μm). The insets show IPSC traces evoked by 1.0 mA stimulation. The IPSC peak amplitude was plotted against the intensity of stimulation for wt and tg mice. The IPSC amplitude was significantly smaller in tg mice, and two-way repeated-measures ANOVA revealed a significant effect of the genotype (p < 0.004). B, EPSCs were recorded in the presence of bicuculline (10 μm). The insets show EPSC traces evoked by 1.0 mA stimulation. The EPSC amplitudes increased with increment of stimulus intensity in both wt and tg mice, and two-way repeated-measures ANOVA failed to show a significant effect of the genotype (p > 0.06). *p < 0.05 and **p < 0.01 indicate significant differences between wt and tg mice at each stimulus intensity, by multiple comparisons using Bonferroni’s test (no asterisks indicate no significant differences).
- Figure 3.
mIPSCs in layer IV pyramidal cells in wt and tg mice (P21–P27). mIPSCs were recoded in the presence of TTX (1 μm). A, Traces of mIPSCs recorded in layer IV pyramidal cells of wt (top) and tg (bottom) mice. Holding potential −60 mV. B, C, Cumulative distributions of the mIPSC peak amplitude (B) and IEI (C) of wt and tg mice. Number of events was 2800 for each.
- Figure 4.
Distribution of inhibitory neurons and their axon terminals in the barrel cortex. Distribution of inhibitory neurons and their axons in the layer IV of the barrel cortex was studied by an immunohistochemical method using anti-GAD antibody. GAD-immunoreactive neurons in wt and tg mice (P21–P24). There was no obvious difference in distribution of GAD-immunoreactive neurons between wt and tg mice. Arrows point to GAD-immunoreactive neurons. Scale bars, 200 μm. Insets show that punctately stained GAD-immunoreactive axon terminals were observed around somata of large cells (indicated by the arrows). Scale bars, 50 μm.
- Figure 5.
IPSCs recorded in layer V pyramidal cells of wt and tg mice (P21–P30). IPSCs and EPSCs evoked by local stimulation were recorded in layer V pyramidal cells of wt and tg mice. A, The IPSC peak amplitude was increased with increments of the stimulus intensity in wt and tg mice. The insets show IPSC traces by 1.0 mA stimulation. B, The EPSC amplitude in tg mice was reduced. The insets show IPSC traces by 10 mA stimulation.
- Figure 6.
IPSCs and EPSCs in layer IV and V pyramidal cells of younger wt and tg mice (P14–P16). A–D, The IPSC and EPSC peak amplitudes of layer IV (A, C) and V (B, D) were plotted against the intensity of stimulation for wt and tg mice at P14–P16. In both layers, the IPSC and EPSC peak amplitudes increased with increments of stimulus intensity in wt and tg mice. The insets show IPSC and EPSC traces by 1.0 mA stimulation. E, Averaged IPSC and EPSC peak amplitudes evoked by 1.0 mA stimulation in P14–P16 (left) and P21–P30 (right) mice. All data are represented as mean ± SEM for n = 10. **p < 0.01, Bonferroni’s test.
- Figure 7.
Developmental changes in ω-Aga-IVA sensitivity of IPSCs in layer IV pyramidal cells. A, B, Time course of the peak IPSC amplitude in response to application of ω-Aga-IVA (200 nm; gray bar) and additional ω-CTx-GVIA (3 μm; white bar). The insets show IPSC traces at the time points indicated by the numbers. ω-Aga-IVA reduced the IPSC amplitude by 20% at P14–P15 (A, left). ω-Aga-IVA reduced the IPSCs amplitude by 45%, and additional ω-CTx-GVIA almost completely blocked IPSCs at P21–P22 (B, left). However, the developmental change of IPSC in ω-Aga-IVA sensitivity was not observed in tg mice (A, B, right).
- Figure 8.
Postsynaptic potentials in layer IV pyramidal cells in response to thalamic stimulation. A, Typical responses of the thalamocortical PSPs in layer IV pyramidal cells of wt (left) and tg (right) mice, with increments of the stimulus intensity. B, Vertical expansion of the thalamocortical PSPs with the 400 μA stimulus intensity, which are identical to those in A. Note that the thalamic stimulation with 400 μA intensity evoked transient depolarization followed by long-lasting hyperpolarization in wt mice (top) but long-lasting depolarization in tg mice (bottom). The early transient depolarization is indicated by Peak, whereas the late long-lasting hyperpolarization and depolarization are indicated by arrowheads. The membrane potentials before the stimulation were set to −60 mV by current injection. Stimulus artifacts were truncated. C, Time course profiles of thalamocortical PSPs with 400 μA stimulus intensity in wt and tg mice. PSP values were calculated as membrane potentials at each time point after stimulation minus those just before stimulation. Peak amplitudes of the early transient depolarization (indicated by Peak) were searched from 2 to 7 ms after stimulation in individual preparations. The time course profiles were significantly different between wt and tg mice (p < 0.02, two-way repeated-measures ANOVA). *p < 0.05, **p < 0.01, Bonferroni’s test between genotype at each time point. D, Stimulus intensity profiles of thalamocortical PSPs at 40 ms after stimulation. The stimulus intensity profiles were significantly different between wt and tg mice (p < 0.03, two-way repeated-measures ANOVA). *p < 0.05, **p < 0.01, Bonferroni’s test between genotypes at each stimulus intensity.
Additional Files
Supplemental data
Files in this Data Supplement:
- supplemental material - Supplementary Figure 1. IPSCs of layer IV pyramidal cells in the primary auditory cortex of wt and tg mice. The insets show IPSC traces evoked by local stimulation (1.0 mA). The IPSC peak amplitude was plotted against the intensity of stimulation for wt (n = 10) and tg mice (n = 10). Two-way repeated measures ANOVA failed to show a significant effect of the genotype (p > 0.6).
