Sumatriptan effects on morphine-induced antinociceptive tolerance and physical dependence: The role of nitric oxide.

Sumatriptan, a 5HT (5-hydroxytryptamine) receptor agonist, showed neuroprotection in different studies. The aim of the present study was to investigate the effect of sumatriptan on morphine-induced antinociceptive tolerance and physical dependence. We also investigated the possible role of nitric oxide (NO) on sumatriptan effects.