Analysis of dopamine release using fast-scan cyclic voltammetry. The amount of dopamine release was determined at five regions within the striatum (at bregma level ∼1.00 to bregma 0.80) including (1) mid-striatum, (2) dorsomedial, (3) dorsal, (4) dorsolateral, and (5) ventrolateral in representative mice from all four groups (see brain slice insert). A , Comparison of peak dopamine released by a single intrastriatal stimulus (200 A, 0.1 ms). Top, Data comparing saline and saline plus exercise mice. There was no significant difference in dopamine release in any region. Middle, Data comparing saline and MPTP groups. There was a significant decrease in dopamine release in MPTP mice and the asterisk represents significant difference compared with saline (p < 0.001). Bottom, Data comparing MPTP and MPTP plus exercise mice. There was a significant increase in dopamine release in the MPTP plus exercise mice at dorsal sites 3 and 4 compared with MPTP mice, and the asterisk represents significant difference (p < 0.05). B , Comparison of dopamine signal (peak and decay) evoked by intrastriatal stimulation. Top, A plot of average time to peak and decay in the dopamine signal at electrode position 4 for MPTP plus no exercise (n = 7, filled circles) and MPTP plus exercise (n = 11, open circles). The intrastriatal stimulus was delivered at the time indicated by the filled triangle (between 0 and 0.8 s). Data points are normalized to the peak-evoked dopamine signal. The middle panel illustrates the decay phase of the graph (shaded area), which was fit with a single exponential function. Best fit for the average data from MPTP plus no exercise mice (solid line) and MPTP plus exercise mice are shown (dotted line). The bottom panel illustrates the averages of the decay constant (k) obtained by the exponential fit of the decay phase for each recording and are shown for each group (mean ± SEM). MPTP plus exercise mice had a significantly lower decay constant compared with MPTP plus no exercise mice (p < 0.05; t test). A similar trend was seen in the saline plus exercise compared with the saline plus no exercise animals (p = 0.13; t test). Exc, Exercise.