Fig. 2.
No net flux plot of dialysate DA data obtained from rats treated repeatedly with the κ-agonist U-69593 (0.32 mg/kg, s.c.) and/or cocaine (20 mg/kg, i.p.). Data were collected under steady-state conditions 3 d after a 5 d repeated drug treatment regimen (once per day). The no net flux plot shows the mean ± SEM gain or loss of DA (DAin −DAout) by dialysis from perfusate containing 0, 5, 20, or 40 nm DA (DAin), and the average linear regression, for each experimental group. An estimate of extracellular DA concentration is given by DAext and is that concentration of DAin from which no DA is gained or lost during dialysis (DAin− DAout = 0). The in vivoEd, an indirect measure of DA uptake, is given in the slope of the line. Data are given by treatment group as follows: ▪ = Veh + Coc (20 mg/kg, i.p.;n = 12); ■ = Veh + Sal (n = 12); ● = U-69+Coc (n = 13); ○ = U-69 (0.32 mg/kg, s.c.) + Sal (n = 10). Cocaine significantly increased Ed, and U-69593 significantly decreased Ed(p < 0.05; main effects identified by two-way ANOVA). No significant group differences inDAext were found.