Recently, both conventional in vivo microdialysis and quantitative in vivo microdialysis under transient conditions were performed to determine whether age-related differences in basal DA exist in the NAcc. Preadolescent (PND 25), early adolescent (PND 35), late adolescent (PND 45) and young adult (PND 60) rats were implanted with cannula and microdialysis probes into the NAcc. Using the conventional approach, artificial cerebrospinal fluid was perfused through the probe and DA was recovered (Philpot and Kirstein, 2004). Using the quantitative approach (adopted from Olson & Justice, 1993) differing concentrations of DA were perfused and the dialysate analyzed to determine levels based on the concentration put in and the concentration recovered (Badanich, Adler and Kirstein, 2006). The concentration that reached steady state (DA in = DA out) was considered the basal level. Both approaches yielded similar age results, with late adolescent animals (PND 45) having significantly higher basal DA levels than adults, but with the conventional method (Philpot and Kirstein, 2004), dialysate DA levels obtained in adolescents were higher than those obtained using the quantitative method (Figure 4; Badanich et al., 2006). Additionally,
