Time-course of antinociceptive effects produced by morphine, oxymorphone and <i>N</i>-methylmorphinans 1, 4 and 6.

<p>The effect of morphine (1.25–5 mg/kg), oxymorphone (0.2–1 mg/kg), and compounds <b>1</b> (0.05–0.5 mg/kg), <b>4</b> (0.5–5 mg/kg), and <b>6</b> (0.1–0.5 mg/kg) in the hot-plate test (A, left panel) and in the tail-flick test (B, right panel). Hot-plate and tail-flick latencies (in seconds) were determined in mice before (0 min) and after s.c. drug administration (30, 60 and 120 min). Data are shown as the mean ± SEM (<i>n</i> = 5–6 mice per group).