Involvement of spinal delta 1-opioid receptors in forced walking stress-induced antinociception in the tail-flick test in mice

Abstract

The purpose of this study was to elucidate the involvement of spinal delta-opioid receptor subtypes in forced walking stress-induced antinociception mice. We first confirmed that forced walking stress produced walking duration-dependent antinociception in mice as determined by the tail-flick test. Intrathecal treatment with 7-benzylidenenaltrexone, a selective delta 1-opioid receptor antagonist, significantly attenuated forced walking stress-induced antinociception. In contrast, intrathecal treatment with naltriben, a selective delta 2-opioid receptor antagonist, had no significant effect on forced walking stress-induced antinociception. Intracerebroventricular treatment with either 7-benzylidenenaltrexone or naltriben had no effect on the forced walking stress-induced antinociception. These results suggest that forced walking stress-induced antinociception is mediated by spinal delta 1-opioid receptors in mice.