Influence of naloxone on analgesic effects of antidepressants in mice.

The present study investigates the effects of a tricyclic (imipramine) and two atypical antidepressants (nomifensine and mianserin ) on nociception to chemical and thermal stimuli in mice. The reversibility of these effects by the opioid antagonist naloxone was also assessed. Imipramine, nomifensine and mianserin produced a significant analgesic effect in both the acetic acid-induced writhing and hot plate tests. The analgesic action of imipramine was influenced by pretreatment with naloxone. These results suggest that different antidepressant drugs are capable of inducing antinociceptive effects in mice, probably mediated by opioid and non-opioid systems.