Bilaterally enhanced dorsal horn postsynaptic currents in a rat model of peripheral mononeuropathy

Surface compound potentials were recorded from the surgically exposed lumbar spinal cord in anaesthetized rats which had had one sciatic nerve loosely ligatured 12-15 days previously, resulting in unilateral allodynia and hyperalgesia, as assessed behaviourally. These cord dorsum potentials were recorded in response to electrical stimulation of the ligatured and non-ligatured sciatic nerve, respectively, on both the ipsi- and contralateral side with respect to the stimulated nerve. Compared to potentials produced by stimulation of the non-ligatured sciatic nerve, electrical stimulation of large diameter fibres proximal to the ligatures resulted in a smaller afferent fibre input arriving at the spinal cord. However, larger net postsynaptic currents in the contralateral dorsal horn and a larger net postsynaptic current per unit of efferent fibre input were found in the ipsilateral and contralateral spinal cord. Such changes may result from structural changes or increased synaptic efficacy in the dorsal horn following peripheral nerve injury.