Spinal neuron sensitization facilitates contralateral input in rats with peripheral mononeuropathy.

The effects of noxious stimulation of one hindpaw on the dorsal horn wide dynamic range (WDR) neurons activity of the opposite side were examined and compared in rats with chronic constriction of one sciatic nerve (CCI), in intact rats and in sham operated rats. Extracellular recordings, were performed in anesthetized, paralyzed rats in the sciatic spinal cord segments (L5-L6). Both the number and the magnitude of the responses were significantly larger in CCI than in intact and in sham rats. The effect was mainly excitatory, only in a few cases was inhibition observed. The relation of the contralateral increased efficacy with the level of excitability of the target neurons is discussed and a role of the potentiated cross transmission in some contralateral pain disorders is hypothesized.