Long term potentiation of single WDR neurons in spinalized rats

We report long-term potentiation (LTP) in single spinal wide dynamic range (WDR) neurons in urethane-anaesthetized spinalized rats with a complete neu romuscular blockade. Peripheral influences were excluded by a complete lido caine block distal to the stimulation site on the sciatic nerve. As previou sly shown A-P fibre evoked responses were not increased by the tetanic stim ulation when there was a neuromuscular blockade during the experiment. Spin alization, excluding influences from supraspinal structures, increased all firing responses, and the LTP of C-fibre evoked responses when calculated i n number of action potentials compared to intact animals and to previous st udies. Furthermore, an LTP of the post discharge was observed after spinali zation. An LTP of the post discharge has previously not been reported. Ther efore, we conclude that LTP in the dorsal horn normally seems to be inhibit ed by descending pathways. (C) 1999 Elsevier Science B.V. All rights reserv ed.