Figure 5. Tetradecanoyl phorbol acetate (TPA) treatment is associated with a dose-dependent decrease in SH-SY5Y MuOR mRNA. SH-SY5Y cells were incubated with TPA at the indicated final concentrations for 4 h. (A) Representative autoradiograms from one experiment. The TPA concentration in the incubation medium is indicated. Control cells received an equal volume of ethanol (1%[vol/vol] final concentration). (B) Graph representing the levels of mu opioid receptor mRNA present in SH-SY5Y cells after incubation with TPA. Data from three independent experiments (n = 8–18 per data point) were normalized to the maximum value in the experiment, pooled, and plotted as the mean +/- SE. **Indicates different from control, at P <or= to 0.01, with other values not significantly different from control as determined by analysis of variance with Dunn's test for comparisons with the control value.