(a) Schematic representation of the in vivo single-cell electrophysiological recording experiments and electrode placement in the LDT in anesthetized animals. (b) iuGC animals present decreased basal activity of LDT neurons in comparison to CTR (nLDT-CTR = 36 cells; nLDT-iuGC = 94 cells). (c) Schematic representation of the in vivo single-cell electrophysiological recording experiments in the VTA with electric stimulation performed in the LDT; and recording electrode placement. (d) The basal activity of the VTA is similar between groups (nVTA-CTR = 40 cells; nVTA-iuGC=32 cells). (e) Electrical stimulation of the LDT (0.5 Hz) induces excitatory and inhibitory responses in VTA neurons. Pie plots represent the percentage of excitatory, inhibitory and no responses of VTA neurons. (e–g) In CTR animals, 50% of neurons present an excitatory response (70% pDAergic, 20% pGABAergic) and 30% present an inhibitory response (21% pDAergic, 50% pGABAergic). iuGC group shows a different profile, with 31% of recorded cells presenting an excitatory response (30% pDAergic, 60% pGABAergic) versus 44% with inhibitory response (57% pDAergic, 29% pGABAergic). (f) Representative examples of rat VTA pDAergic and pGABAergic neuronal waveforms. (g) Firing rate and waveform duration were used to classify single units into 3 types of neurons. (h) Percentage of each putative neuronal population presenting excitation, inhibition or with no response to LDT stimulation. There is a shift in the percentage of putative DAergic and GABAergic neurons presenting excitatory and inhibitory responses. Numbers in bars represent number of cells in each category. (i, m) Peristimulus time histograms (PSTHs) show LDT-evoked responses of VTA dopamine neurons; (i) excitation; (m) inhibition. (j) VTA neurons that display an excitatory profile in response to LDT electrical stimulus present increased latency to fire in iuGC animals. (k) The magnitude and (l) duration of response of VTA neurons is reduced in iuGC animals. (n) VTA neurons that display an inhibitory response in response to LDT electrical stimulus do not show differences in the latency to fire in both groups. (o) The magnitude of response of inhibited neurons of the VTA is increased in iuGC animals, with no differences in (p) the duration of inhibition in VTA neurons upon LDT stimulation. pDAergic: putative dopaminergic neurons; pGABAergic: putative GABAergic neurons. Data is represented as mean ±s.e.m. *p<0.05, **p<0.001, ***p<0.0001.