Figure 2. Striatal DA signals evoked by midbrain and cortical inputs. A, Example of the fluorescence pattern (bottom) observed in a sagittal brain slice from a DATIRES-Cre+ mouse injected with DIO-ChR2-EYFP in the midbrain (top). B, Example of the fluorescence pattern (bottom) observed in a sagittal brain slice from a C57Bl6/J (DATIRES-Cre–) mouse injected with ChR2-EYFP in the PrL or IL cortex (top). Inset, A more medial slice with the site of injection. C, Representative DA transients, current–voltage (CV) plots, and color voltammograms when evoked by electrical stimulation (eDA, left), optogenetic stimulation of DAN fibers (DAN-oDA, middle), or optogenetic stimulation of PFC inputs (PFC-oDA, right). All three CV plots show the electrochemical profile of DA oxidation. Scale bar, 100 nM. D, A sagittal brain section modified from the Mouse Brain Atlas (Franklin and Paxinos, 2007) showing the FSCV recording sites from mice injected with ChR2-EYFP in the PrL (filled) and IL (empty) cortex. E, The oxidation (top) and reduction (bottom) voltages from the CV plots of eDA (left), DAN-oDA (middle), and PFC-oDA (right) were plotted as average with SEM. Open and filled circles represent individual values. F, DA peak concentrations and G, decay time constants of eDA (left), DAN-oDA (middle), and PFC-oDA (right) were plotted as average with SEM. Open circles represent individual values. For PFC-oDAs, the same color code was applied as in D for PrL and IL according to injection location. E–G, Data points include experiments where electrical and optogenetic stimulation was delivered alternatingly in the same slice or in different slices (see Materials and Methods). **p < 0.01, ***p < 0.001. LV, Lateral ventricle; DS, dorsal striatum; ac, anterior commissure; AcC, accumbens core; AcSh, accumbens shell; VP, ventral pallidum; PBP, parabrachial pigmented nucleus; SNR, substantia nigra reticulata; Th, thalamus; Tu, olfactory tubercle. n.s., not significant.