Western-blotting analysis of TH phosphorylated (p) at Ser 31 (A) or Ser40 (B)/total (t)TH ratio in the nucleus accumbens (NAc) 60 min after saline (Sal, S) or naloxone (Nx, N) administration to placebo (P) or morphine (M) dependent rats pretreated with Tween 80 (Tw, V) or CP-154,526 (20 mg/kg, i.p., CP) (A, B).

<p>The immunoreactivity corresponding to TH phospho-Ser31 or TH phospho-Ser40 is expressed as a percentage of that in the control group defined as 100% value. Data are the mean±SEM (n = 6). **p<0.01, versus the morphine dependent group receiving saline instead of naloxone; ++p<0.01 versus the placebo group injected with Tw+Nx; &&&p<0.001 versus morphine+Tw+Nx.