Morphine antinociception (%MPE) on the hotplate test (left panel), tail withdrawal test (middle panel) and paw pressure test (right panel) in gonadally intact male rats treated for 28 days with vehicle (VEH), testosterone (T), dihydrotestosterone (DHT), or stanozolol (STAN). Each point is the mean ± 1 S.E.M., N = 25 (vehicle group) and N = 12–14 rats (AAS groups). The morphine ED50 was significantly greater in the DHT group than in the vehicle group on the hotplate test only.