Figure 1: Percent maximum possible effect (%MPE) (a) and naloxone-precipitated withdrawal jumping (b) following different treatments. In hot plate latency testing (a), Sal-no morphine (Sal-no mor) group received saline (s.c.) and was tested for hot plate latency 30 min later. All other groups received their treatment and were then given morphine (10 mg/kg, s.c.) followed by hot plate latency testing 30 min later. See Table 1 for details on the morphine treatment paradigm. # , versus saline-no mor, * , versus saline with morphine given 30 min after. per treatment. In naloxone-precipitated withdrawal (b), mice received either escalating dose of morphine or morphine pellet for 24 h or 7 days or corresponding controls and then received naloxone (1 mg/kg, s.c.) to precipitate withdrawal, which was determined by counting the mean number (±SEM) of jumps over the next two h. The number of jumps in control treated mice was too small to be seen on the figure. *** , versus escalating dose. # , versus PM24h. per treatment.