OXYTOCIN MODULATES THE EFFECTS OF GALANIN IN CARRAGEENAN-INDUCED HYPERALGESIA IN RATS

In the present study we have investigated the effects of galanin and/o r oxytocin on carrageenan-induced hyperalgesia, the relationship betwe en oxytocin and galanin-containing nerve fibers in the spinal cord and the influence of galanin on oxytocin secretion. Galanin (1 mug) given intrathecally (i.t.) decreased significantly the mechanical nocicepti ve threshold of the carrageenan-treated hindpaw, with no significant e ffect on thermal nociception. The decrease in the mechanonociceptive t hreshold exerted by galanin was modulated by oxytocin (1 mug, i.t.) ad ministered simultaneously. There was a close relationship between gala nin- and oxytocin-immunoreactive fibers in the dorsal horn of the thor acic spinal cord, although there was no evidence for colocalization. G alanin 0.1 and 1 mug given intracerebroventricularly or intraperitonea lly significantly decreased the oxytocin level in plasma 60 min after injection. Taken together, these data indicate that galanin may contri bute to mechanical hyperalgesia by inhibiting the release of oxytocin from nerve terminals in the spinal cord and that oxytocin may be a pot ential analgesic agent.