Spinally delivered nociceptin/orphanin FQ reduces flinching behaviour in the rat formalin test

Abstract

The aims of this study were to investigate the dose-dependent effects of spinally delivered nociceptin (0.3, 1, 3.3 and 10 nmol) on flinching behaviour in the rat formalin test and whether these effects were influenced by the concomitant systemic administration of naloxone (3 mg/kg, i.p.). The effect of the highest nociceptin dose differed statistically from vehicle, 0.3 and 1 nmol nociceptin. Following the administration of 1, 3.3 or 10 nmol nociceptin mean total flinches decreased dose-dependently. The effects of 10 nmol nociceptin were not reversed by a high dose of naloxone. We observed a decrease in flinching behaviour with intrathecally to the lumbar enlargement delivered nociceptin and conclude that nociceptin has antinociceptive effects in the rat formalin test.