Fig. 2

p-Cresol treatment alters VTA dopamine neurons excitability. A Differential interference phase contrast representative image of a dopamine neuron in the lateral VTA, as seen in the electrophysiology setup. Dotted circle delineates the neuronal soma and arrow points to the patch-clamp pipette. Scale bar: 10 μm. B Representative voltage response to a 300 pA hyperpolarizing current step in a putative dopamine neuron. Voltage peak sag mediated by Ih currents were used to identify dopamine neurons. C Representative traces of dopamine neuron activity in patch-clamp experiments after a 200 pA current injection. D Number of action potentials evoked by current injection in current-clamp experiments (n = 5 animals/group, 19 cells recorded for control, 23 cells recorded for p-Cresol); 2-way ANOVA: p (Treatment) = 0.0066, p (Current) < 0.0001, p (Treatment × Current) = 0.0006; Šidák’s post hoc tests for treatment effect: *p < 0.05, **p < 0.01, ***p < 0.001. E Rheobase, minimal electric current required to evoke an action potential (n = 5 animals/group, 19 cells recorded for Control, 23 cells recorded for p-Cresol); Mann-Whitney U-test: *p < 0.05. F Representative traces of spontaneous miniature excitatory post-synaptic currents (sEPSC). G Cumulative frequencies of sEPSC absolute amplitude (n = 5 animals/group, > 2500 events/group); Kolmogorov-Smirnov test: ****p < 0.0001. H Mean absolute amplitude of sEPSC; Mann-Whitney U-test: ****p < 0.0001. I Cumulative frequencies of sEPSC frequency (n = 5 animals/group, > 2500 events/group); Kolmogorov-Smirnov test: ****p < 0.0001. J Mean frequency of sEPSC; Mann-Whitney U-test: ****p < 0.0001. D, E Data are shown as means ± SD. H, J Data are shown as means ± SEM