Excitatory effects of galanin in the spinal cord of intact, anaesthetized rats

The effects of intrathecal galanin on the activity of single wide dynamic range (WDR) spinal dorsal horn neurones were analyzed in anaesthetized adult rats. A beta-, A delta- and C-fibres were activated by transcutaneous electrical stimulation wh ich also induced wind-up and post-discharge. Galanin dose-dependently (0.15-15 nmol/50 mul) enhanced A delta -and C-fibre evoked responses, post-discharge and wind-up. Application of (D-Thr(6), D-Trp(8,9), 15-ol)-galanin (1-15), a putative antagonist, did not attenuate the enhanced effects evoked by galanin. (D-Thr(6), D-Trp(8,9), 15-ol)-galanin (1-15) applied alone (0.3-30 nmol/50 mul) to a separate population of neurones inhibited AP responses but enhanced post-discharge and wind-up in a similar pattern to galanin. Thus, (D-Thr(6), D-Trp(8,9), 15-ol)-galanin (1-15) behaved as an agonist in the present experiments. In conclusion, in the spinal cord of the anaesthetized rat, galanin has a purely pro-nociceptive role, since it enhanced responses evoked by high-threshold fibre stimulation, along with post-discharge and wind-up of WDR neurones. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.