Panels (a) and (b) show average Cmax values for cocaine and dopamine, respectively, as a function of the rate of i.v. cocaine infusion. The time to reach peak concentrations (Tmax) of cocaine (c) and dopamine (d) in the dorsal striatum is shown as a function of the rate of i.v. cocaine delivery. Panels (e) and (f) show the time interval before cocaine and dopamine concentrations were significantly greater than baseline levels (> 2 standard deviations above baseline), as a function of the rate of i.v. cocaine delivery. All values are mean ± SEM. n = 7 rats/infusion rate. *P < 0.05 compared to 90 s. nM, nanomoles/liter. s, seconds.