(A) PSCs elicited by single pulse photostimulation in the mdStr (blue) and ldStr (green) before (Pre) and after sulpiride application (Sul, red). Subtraction of traces (bottom) revealed the sulpiride-sensitive D2R PSC. (B) Average amplitudes of IPSCs and EPSCs, before and after sulpiride. Comparison between pre and post sulpiride: mdStr IPSC, p=0.000; ldStr IPSC, p=0.003; mdStr EPSC, p=0.004; ldStr EPSC, p=0.006 (paired t-test). mdStr: n = 8 cells from five animals, ldStr: n = 9 cells from six animals. (C) Average PSC charge transfer in the 1.5 s post-stimulus window before sulpiride application, and the sulpiride-sensitive component in the same cells. Comparison between mdStr and ldStr: charge, p=0.003; sulpiride-sensitive component, p=0.67 (Welch’s t-test). (D) DA release was measured with FSCV, in response to single pulse (top, thin traces) and train (bottom, thick traces) photostimulation in the two subregions. Representative cyclic voltammograms are shown in the inset. (E–G) Normalized peak amplitude, decay time constant, and the ratio of train to single stimulation of DA release are plotted. Dots are measurements in single slices. Comparison between mdStr and ldStr: single peak, p=0.83; train peak, p=0.79; single tau, p=0.81, train tau p=0.37, train/single ratio p=0.33, paired t-test. n = 5 slices from five animals. (H) In the ldStr (green), after blocking the D2R component of the slow response with sulpiride (red), CNQX + APV (gray) had no impact on the slow response, but blocked the initial fast inward iGluR component (traces in dashed box are shown on an expanded time scale below); SR69951 blocked the remaining initial fast outward GABAA component (black trace). n = 6 cells from three animals. (I) Average amplitudes of fast and slow EPSCs before and after CNQX + APV, in the continuous presence of sulpiride. Comparison between pre and post iGluR antagonists: fast EPSC, p=0.022; slow EPSC, p=0.90, paired t-test. (J) Isolation of slow EPSC in ldStr ChIs after blockade of D2, GABAA and iGlu receptors, with single pulse photostimulation (at 0.1 Hz; above), and effect of train photostimulation on firing (5 pulses at 20 Hz; bottom). (K) Firing z score during and after train photostimulation, prior to (Ctrl) and after application of a cocktail of D2 + GABAA + iGluR antagonists, recorded from different sets of neurons. Ctrl data are the same as shown in Figure 1C. Ctrl: n = 15 cells from nine animals. Antagonists: n = 11 cells from seven animals. Comparison between pre and post antagonists: during stim p=0.000, post stim p=0.25, independent sample t-test. Numbers in parentheses in B, C, I, K indicate numbers of cells recorded and in E indicate numbers of slices recorded. Dots in bar graphs show the average for each recorded cell. Sample PSC traces are the average of 10 consecutive traces. *, ** and *** indicate p<0.05, p<0.01 and p<0.001, respectively.