Figure 4.

VTA glutamatergic neurons release GABA in the DG. A, Schematic showing the injection procedures for retrograde tracing or for whole-cell recordings in VGLUT2-Cre mice (as done in Fig. 1A,H for GAD65-Cre mice). B, CTB555 injection site in the dDG. C, High-magnification image of the retrogradely labeled neurons in the VTA, some of which colocalize with EYFP. D, Schematic localization of retrogradelylabeled cells and the proportion of CTB-positive neurons colocalizing with EYFP in VGLUT2-Cre mice. E, Graph showing the average amplitude (±SEM) of the light-evoked PSCs recorded in the GCL of VGLUT2- or GAD65-Cre mice as a function of their connectivity. F, Example traces showing the light-evoked PSC recorded in a granule cell at baseline and after bicuculline alone (Bic) or together with NBQX (Bic+NBQX). G, Peak amplitude time course from the same example neuron in F. H, Residual current amplitude after Bic (n = 8) or Bic+NBQX (n = 7) application, shown as a percentage of the baseline current amplitude. I, Sample traces before and after the application of Bic or NBQX alone. J, Effect of Bic or NBQX alone on the time to peak (n = 8,9), decay time (n = 7,11), onset latency (n = 8,11), and PPR (n = 8,11) of the light-evoked currents.