Antinociceptive effects induced by desipramine and fluoxetine are dissociated from their antidepressant or anxiolytic action in mice

This study aimed to evaluate the relationship between some aspects of experimental depression, anxiety and the antinociceptive effects of fluoxetine and desipramine in mice. Acute administration of fluoxetine and desipramine (5, 10 and 20 mg/kg, i.p.) showed significant antinociceptive effects in the hot-plate test and against the early and late phase of the mouse formalin test, dissociated from its antidepressant and anxiolytic effects as measured in the forced swimming and in the plus-maze tests, respectively. Neither fluoxetine nor desipramine, at the doses tested, produced significant effects on locomotor activity. Furthermore, both compounds were ineffective in the tail-flick phasic model of nociception. In conclusion, the results suggest that without the distinction of serotonergic and noradrenergic contributions, the acute antinociceptive effects of fluoxetine and desipramine in mice are independent of their sedative, antidepressant and anti-anxiety properties.