Fig. 5. The effect of long-term treatment with propofol on [3H]norepinephrine uptake. (A ) Time course of preincubation with propofol (1 μm) for [3H]norepinephrine uptake. After preincubation with or without propofol for the period indicated, the cells were cultured for another 3 h in propofol-free medium and then incubated at 37°C for 15 min in the presence of [3H]norepinephrine (500 nm). The values of the control group at 6, 12, and 24 h were 1.3 ± 0.2, 1.2 ± 0.2, and 1.2 ± 0.1 pmol · 4 × 106cells−1· min−1, respectively. (B ) Effect of preincubation with various concentrations of propofol on [3H]norepinephrine uptake. The results are the mean (±SD) of four separate experiments conducted in duplicate. *P < 0.05 compared with control.