Figure 8.

The pause in CIN firing evoked by SNc neuron stimulation is mediated by D₂ receptors. A, Representative cell-attached recording from CINs obtained from a control Dat^IRES-Cre;Ai32 mouse (top, black trace) or a reserpine-treated littermate (bottom, red trace) upon optogenetic stimulation of nigrostriatal afferents (blue arrows). B, Population perievent spike histogram (normalized to baseline) for all CIN recordings obtained in control (n = 14, black) and reserpine-treated slices (n = 12, red) following light stimulation of SNc axons (blue arrow). Solid lines represent the mean, shaded regions the SEM. C, E, Example cell-attached recordings from CINs in slices of dorsal striatum expressing ChR2 in SNc axons before (baseline, black traces) or after bath perfusion of the GABA_A receptor blocker SR95531 (10 μm; C, red trace) or the D2 receptor antagonist sulpiride (1 μm; E, red trace). D, F, Same as B for extracellular CIN recordings before (black) and after (red) bath application of SR95531 (n = 9, D) or sulpiride (n = 8, F). Note that the light-evoked suppression of firing is sensitive to D₂ receptor block, but not GABA_A receptor antagonism.