Antinociceptive role of galanin in periaqueductal grey of rats with experimentally induced mononeuropathy.

The present study was performed in rats with experimentally induced mononeuropathy after left common sciatic nerve ligation. The hindpaw withdrawal latencies to thermal and mechanical stimulation increased significantly after intra-periaqueductal grey injection of 2 or 3nmol, but not 1nmol of galanin in rats with mononeuropathy. Intraperitoneal administration of 4.5mg/kg morphine induced significant increases in hindpaw withdrawal latencies to both noxious stimulation, which were attenuated by following intra-periaqueductal grey injection of 2nmol of the galanin antagonist galantide. Furthermore, the antinociceptive effect induced by intra-periaqueductal grey injection of 26.6nmol of morphine was attenuated significantly by following intra-periaqueductal gray administration of 2nmol of galantide. The results demonstrated that in periaqueductal grey galanin plays an antinociceptive role in rats with mononeuropathy and galanin is involved in the mechanisms of opioid-induced antinociception.