Fig. 3

Dormant neurons exist in intact tissue and exhibit a specific cytosolic structural organization. a Typical in situ recordings obtained under current clamp from a dormant (top) and a spiking pyramidal cell (bottom). The former is characterized by the conspicuous absence of action potentials. Note in spiking cells, but not dormant cells, spontaneous synaptic activity is present. b–c Summarized data of membrane capacitance (C _m; dormant n = 18, spiking n = 13; t ₍₁₂₎ = 5.56 Welch-corrected p < 0.001) and input resistance (R _in; dormant n = 18, spiking n = 13; t ₍₁₇₎ = 9.99 Welch-corrected p < 0.001) between the two cell types in situ. d Similar to behaviour observed in vitro, under voltage-clamp (–60 mV) conditions, dormant neurons exhibited negligible current and a quasi-linear current-voltage relationship. e Representative images of a biocytin (0.5–1 %) labelled dormant (left) and spiking neuron (right), illustrating their notable difference in ability to label dendrites. Note that the lack of dendritic labelling is not due to the fact that dormant neurons lack dendrites, as dendrites could always be visualized under DIC microscopy (left; yellow arrows). Dormant DIC and biocytin images are of the same cell. f Summary data of the total dendritic length labelled between the two phenotypes (t ₍₅₎ = 4.42 Welch-corrected p = 0.0068; n = 7 and n = 6 respectively). g Representative images of both dormant (left) and spiking (right) neurons when the lipid-binding amphipathic dye FM1-43 (3–10 μM) was included in the pipette. h Summary data of the FM1-43 fluorescence signal between the two phenotypes (t ₍₁₉₎ = 3.30, p = 0.0037; n = 14 dormant and n = 7 spiking). e and g scale bars = 10 μm. ** p < 0.01; ***p < 0.001