Figure 2.

Mouse SN neurons displayed four different types of dopamine responses. Relative frequencies of four identified different dopamine-responses, and anatomical locations of MEA-recorded neurons from juvenile (A) and adult (B) mice. Experiments, MEA recordings, and data analysis described in Figure 1. Data were derived from juvenile (~PN13) and adult (~13W) C57BL/6J mice, recorded in ACSF containing 2.5 mM glucose. Left panels: SN neurons were classified according to their dopamine responses in DA-excited (44%, juveniles, 42% adults) and DA-inhibited (56% juveniles, 58% adults) cells. DA-excited cells were subclassified in neurons with (blue) and without (“silent,” red) spontaneous activity before DA-application. DA-inhibited cells were subdivided in neurons with (“desens,” grey) and without (white) prominent desensitization of dopamine responses over time. Numbers of DA-excited neurons with activity before DA-application was significantly higher in adults (p = 0.0025). Right panels: Maps displaying the anatomical locations of the DA-excited (upper) and DA-inhibited (lower) neurons within the SN, on caudal (left), medial (middle), and rostral (right) coronal slices. Maps are derived form the Paxinos mouse brain atlas (reproduced with permission from Elsevier Ltd.), figures 56, 57, 60 (Bregma: −3.08, −3.16, −3.52), respectively (Paxinos and Franklin, 2001). All data and statistics are detailed in Supplementary Table 1.