Figure 2.

Voltage-dependent conductance increase during scratching. A, A train of short (100 ms) hyperpolarizing current pulses were injected into a motoneuron just before and during scratching in CC mode. B, V_m during current pulses was aligned (light gray) and averaged (dark gray). The V_m deflection caused by current injection is larger at rest than during scratching, indicating conductance increase during scratching (n = 14, p = 1.2 × 10⁻⁴, Wilcoxon signed rank test). C, The conductance of the same motoneuron was evaluated during scratching when V_m was hyperpolarized in VC recordings. Holding V_m was changed between −70 and −60 mV at 10 Hz. D, Episodes of I_m at the two V_m levels were aligned (light yellow) and averaged (dark yellow). The difference in I_m at the two V_m levels is larger during scratching than at rest, indicating conductance increase during scratching (n = 14, p = 1.2 × 10⁻⁴, Wilcoxon signed rank test). E, F, Conductance also increased during scratching when V_m was hyperpolarized by a steady hyperpolarizing holding current in CC recordings (n = 7, p = 0.016, Wilcoxon signed rank test). G, Smaller conductance increase (Δg) was observed during scratching when motoneurons were hyperpolarized in VC recordings (n = 14, p = 1.2 × 10⁻⁴, Wilcoxon signed rank test). H, In line, smaller Δg during scratching was also found with the hyperpolarizing holding current in CC recordings (n = 7, p = 0.016, Wilcoxon signed rank test). Red open circles in B, D, and F–H represent mean.