Reversal by serotonergic agents of reserpine-induced hyperalgesia in rats

Reserpine (4 mg/kg) induced a time-dependent reduction in pain threshold (hyperalgesia) as observed by the tail-flick technique in rats. Serotonin, its precursor 5-hydroxytryptophan or the receptor agonist, quipazine reversed the reserpine-induced hyperalgesia. On the other hand, piribedil, amantadine, imipramine or desipramine treatment failed to reverse the reserpine-induced hyperalgesia. Similarly, intracerebroventricular administration of dopamine or noradrenaline also had no effect on reserpine-induced hyperalgesia. These observations not only suggested a role of serotonin in hyperalgesia but also that reserpine hyperalgesia is suitable for selective study of serotonin-mediated responses in rats.