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Fig. 1 | BMC Biology

Fig. 1

From: Somato-dendritic decoupling as a novel mechanism for protracted cortical maturation

Fig. 1

Reduced TeA excitability despite continued growth. a Neurons of various ages were transfected with an eGFP plasmid for morphological analysis (Oc1, n = 214; Hip, n = 213; TeA, n = 289). bc Histograms showing neuron size distribution in Oc1, Hip, and TeA at DIV3 b and DIV20 c. The growth time course varied by culture type as a two-way ANOVA revealed a significant main effect of culture type (F(2,698)=37.45, p < 0.0001; Two-way ANOVA) and culture age (F(5,698)=68.21, p < 0.0001; Two-way ANOVA) on total neurite length. There was also a significant interaction between culture type and age (F(10,698)=11.39, p < 0.0001; Two-way ANOVA). d Images of GFP-labelled spines at 100× magnification from DIV20 cultures. Scale bar = 5 μm. e Summarized data for spine density at DIV20. The total dendrite length used for spine densitometry: TeA = 1803 μm; Hip = 1038 μm; Oc1 = 840 μm (Hip, n = 10; TeA, n = 11; Oc1, n = 6). f The percentage of stubby (F (2,84) = 21.19; p < 0.0001; one-way ANOVA), thin (F (2,84) = 1.55; p = 0.22; one-way ANOVA), and mushroom-shaped (F (2,84) = 29.34; p < 0.0001; one-way ANOVA) spines per neurite for different regions. * p < 0.05. g Voltage recordings obtained under current-clamp from a TeA dormant pyramidal cell (top), a TeA spiking pyramidal cell (middle), and a hippocampal spiking pyramidal cell for comparison (bottom) during depolarization. Current pulses were injected from a holding or resting potential of around –60 to –70 mV. Detailed electrophysiological characterization revealed input resistance (5.01 ± 1.1 GΩ n = 9 vs. 0.30 ± 0.08 GΩ n = 10; t (9) = 4.12 Welch-corrected p = 0.003) and capacitance (4.1 ± 0.3 pF n = 9 vs. 105.2 ± 21.8 pF n = 10; t(9) = 4.64 Welch-corrected p = 0.001) between phenotypes are significantly different. Note that given the order of magnitude difference in input resistance between dormant (GΩ) and spiking (MΩ) cells, there was also order of magnitude difference in current step amplitude (e.g. 5-pA steps vs. 50-pA steps). Traces are representative of recordings during the TeA growth phase (DIV10–23). h Significantly more TeA pyramidal cells are dormant. DIV7–10; Oc1 significantly lower than both TeA and Hip p < 0.0001. DIV18–23; Oc1 and Hip significantly lower than TeA p < 0.0001 and p = 0.0019 respectively. p values determined by a Fisher’s exact test on observed phenotype frequency. *p < 0.05; **p < 0.01

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