Fig. 3

The capacity of cladribine to affect neurons of the primary auditory cortex. A mRNA expression of deoxycytidine kinase (DCK) was quantified by quantitative polymerase chain reaction (qPCR) in magnetic-associated cell-sorted (MACS) neurons, compared to macrophages (macroph.; CD45^highCD11b^high), CD3⁺CD4⁺ and CD19⁺ lymphocytes. Platelets served as negative control. Results were normalized to expression levels in macrophages and are depicted as 2^−∆∆Ct values (n = 9 for macrophages, n = 5 for all other cell types, Kruskal–Wallis test). B–F All electrophysiological recordings were obtained at d_max by current-clamp mode (B–D) or voltage-clamp mode (E + F). Four mice were examined per experimental group. B Representative traces recorded at a potential of − 60 mV (set by DC current injection) in current-clamp mode from one animal. A depolarizing current step of + 160 pA triggered the generation of action potentials (APs) in all experimental groups. C Mean bar graph indicating the number of APs generated in response to depolarizing steps of increased intensity ranging from + 20 to + 160 pA. The number of generated APs increased with increasing depolarization under all experimental conditions. Statistically significant differences were obtained starting from + 100 pA (two-way ANOVA, F (2.59) = 5.061, p = 0.0094, n = 23—naïve ctrl, 14—vehicle, 25—cladribine). D Resting membrane potential (in mV; a) and input resistance (in MΩ; b) of neurons of the auditory cortex are depicted indicating no differences between vehicle- vs. cladribine-treated EAE mice compared to naïve controls (unpaired Mann–Whitney U test, p > 0.05, n = 23—naïve ctrl, 14—vehicle, 24—cladribine). E Effects of oral treatment with cladribine on glutamatergic transmission in voltage-clamp mode recorded as excitatory postsynaptic currents (EPSCs). Upon EAE induction, the number of EPSCs (a) increased significantly compared to naïve control (unpaired Mann–Whitney U test, p = 0.0401, n = 28—naïve ctrl, 16—vehicle). Upon cladribine treatment, a trend for a reduction in EPSCs compared to vehicle-treated mice was observed, although not reaching significance (unpaired t test, p = 0.0751, n = 16—vehicle, 19—cladribine). Exemplary electrophysiological traces of voltage-clamp recordings (b) show exemplary EPSC events in recorded neurons from naïve control, vehicle-treated and cladribine-treated EAE mice. F Bar graph illustrating the number of inhibitory postsynaptic currents (IPSCs; a indicating that neither the experimental EAE itself nor oral cladribine treatment did significantly affect the GABAergic transmission (unpaired Mann–Whitney U test, p > 0.05, n = 19—naïve ctrl, 11—vehicle, 16—cladribine). Representative electrophysiological traces of voltage-clamp recordings of IPSCs (b) from all three experimental groups. p > 0.05 = ns, p < 0.05 = *, p < 0.01 = **