(A) Example traces for H-Reflex recordings in mice; the first major deflection is the motor response (M-wave) upon anterograde sciatic nerve stimulation, the second is the H-Reflex after monosynaptic transmission in the spinal cord followed by a polyphasic F-wave.1st and 10th trace of 10 consecutive stimuli are shown for the indicated frequencies. Note that H-Reflex amplification is fourfold higher than for the M-wave. The H-Reflex is unchanged after 10 serial stimuli at 0.1 Hz stimulation, whereas it is completely abolished (100% depression) after 10 stimuli at 10 Hz (post-activation depression, primarily mediated by local GABAergic interneurons). (B) Post-activation depression of the H-Reflex in Cln3Δex1-6 and wt mice was tested at the age of 7 and 14 months and was unchanged at both time points at all investigated stimulation frequencies. Note, that the depression of H-Reflex is shifted to higher frequencies in both genotypes at higher age of 14 months, indicating age-dependent changes within the spinal networks in both groups (7 months n = 12 recordings from 10 mice vs. 14/13, 14 months n = 16/10 vs. 13/8; Two-way ANOVA). (C) Example traces for recordings of dorsal root potentials (DRP) in mice in-vivo as a direct measurement of spinal GABAergic presynaptic inhibition. The upper trace shows a recording of the DRP after a single stimulus, the lower trace shows the DRP after three stimuli demonstrating temporal summation. Arrows indicate electric stimulations. (D) Peak amplitudes of DRP after a single stimulus and the ratio of peak amplitudes after time-dependent summation vs. single stimulation are not significantly different in Cln3Δex1-6 and wt mice at both analyzed time points indicating unchanged spinal presynaptic inhibition (7 months n = 14 recordings from 8 mice vs. 17/8, 14 months n = 17/9 vs. 10/6). Exact p values, dispersion and precision measures are provided in Supplementary file 2.