Fig. 5.

Reversal of chronic morphine tolerance and dependence by haloperidol in mice. Separate groups of six mice received morphine (10 mg/kg s.c.) or an equal volume of saline twice daily for 5 days. Haloperidol dose-dependently reversed the established morphine-antinociceptive tolerance (A) and naloxone (10 mg/kg i.p.)-precipitated withdrawal jumping (B). Data are expressed in mean ± S.E.M. ***, p < 0.001 compared with the saline group; #, p < 0.05; ###, p < 0.001 compared with the morphine (MS) alone group.