Fig. 12.

Effects of the mu agonist methadone, the kappa agonist salvinorin A, and the delta agonist SNC80, on ICSS in rats. Abscissae: frequency of brain stimulation in Hz (log scale). Ordinates: ICSS rate expressed as %MCR. Graphs show illustrative data from dose-effect studies conducted with each drug. Effects of methadone were determined in opioid-naive subjects and again in the same rats during treatment with 3.2 mg/kg per day morphine (opioid-experienced subjects). Filled points show drug effects significantly different from vehicle as determined by two-way ANOVA and the Holm-Sidak post hoc test (P < 0.05). Data sets are published for methadone (Altarifi et al., 2013), salvinorin A (Negus et al., 2012a), and SN80 (Negus et al., 2012b).