Figure 6.

Excitability of primary sensory neurons in the TG of mSOD1 mice. a, Schematic showing the trigeminal sensory nuclei along the midbrain-brainstem regions. Primary 1a afferent neurons in the TG (red dashed rectangle) were acutely dissociated, and whole-cell current-clamp recordings were performed. b, Top left, Example showing NeuN stain (green) used to identify the dissociated TG neurons. Top right, Example of a dissociated TG neuron filled with Texas red 568 dye during whole-cell recording. Bottom left, Merged image. Bottom right, Bright field (BF) image. Scale bars, 50 μm. c, TG neurons were classified into three types: Aβ, Aδ, and C (for criteria, see Results). Open arrows indicate membrane sag during a 1 s hyperpolarizing step pulse in Aβ and Aδ types. Black arrow indicates a hump in Aδ action potential. d, Percentage of the subtypes of TG neurons in WT and mSOD1 mice are not significantly different. e, Inset, The current (I_Threshold) and voltage (V_Threshold) thresholds for action potentials in WT (blue) and mSOD1 (red) TG neurons. Dot plots represent comparison of these properties between WT (blue) and mSOD1 (red) within the Aβ and Aδ groups with no statistical significance. f, Representative membrane voltage responses to increasing levels of 1 s current injection (bottom traces) in repetitively firing WT and mSOD1 TG neurons (both Aδ type). g, Spike frequency-injected current responses in all the Aδ TG neurons that showed repetitive firing. h, Autocorrelation function of membrane potential in WT (left) and mSOD1 (middle) TG neurons; second peaks (arrows) are highlighted. Right, Dot plots represent the second peaks for all the cells with no significant difference between WT (blue) and mSOD1 (red) TG neurons. i, Bar charts represent the age distribution of the mice, including 8 WT mice (n = 36) and 7 mSOD1 mice (n = 27), where n is the number of cells for all the data presented in e–h.