Influence of naloxone on the antinociceptive effects of some antidepressant drugs.

The antinociceptive effects of tricyclic and atypical antidepressants were studied using the rat tail mechanical method. Clomipramine produced analgesia at the doses of 30 and 40 mg/kg, desimipramine at 10, 20 and 40 mg/kg, maprotiline at 20 and 30 mg/kg, mianserin at 30 mg/kg, nomifensine at 1, 2.5 and 5 mg/kg, indalpine at 10, 20 and 40 mg/kg, viloxazine at 60 and 80 mg/kg. Naloxone (0.8 mg/kg) abolished the antinociceptive action of these antidepressant drugs. These results suggest that the antinociceptive activity of these six antidepressant drugs in acute experimental pain could involve opiate mechanisms.