ABSTRACT
Mechanisms underlying central neuropathic pain are poorly understood. Although glial dysfunction has been functionally linked with neuropathic pain, very little is known about modulation of pain by oligodendrocytes. Here we report that genetic ablation of oligodendrocytes rapidly triggers a pattern of sensory changes that closely resemble central neuropathic pain, which are manifest before overt demyelination. Primary oligodendrocyte loss is not associated with autoreactive T- and B-cell infiltration in the spinal cord and neither activation of microglia nor reactive astrogliosis contribute functionally to central pain evoked by ablation of oligodendrocytes. Instead, light and electron microscopic analyses reveal axonal pathology in the spinal dorsal horn and spinothalamic tract concurrent with the induction and maintenance of nociceptive hypersensitivity. These data reveal a role for oligodendrocytes in modulating pain and suggest that perturbation of oligodendrocyte functions that maintain axonal integrity can lead to central neuropathic pain independent of immune contributions.
Subject(s)
Adaptive Immunity/immunology , Axons/pathology , Immunity, Innate/immunology , Neuralgia/pathology , Oligodendroglia/physiology , Spinal Cord Dorsal Horn/pathology , Spinothalamic Tracts/pathology , Animals , Astrocytes , Axons/ultrastructure , B-Lymphocytes , Mice , Microglia , Microscopy, Electron , Neuralgia/immunology , Nociception , Oligodendroglia/metabolism , Spinal Cord/pathology , Spinal Cord/ultrastructure , Spinal Cord Dorsal Horn/immunology , Spinal Cord Dorsal Horn/ultrastructure , Spinothalamic Tracts/immunology , Spinothalamic Tracts/ultrastructure , T-LymphocytesABSTRACT
Central pain syndrome (CPS) is defined as pain associated with a lesion of the CNS and is a common consequence of spinal cord injuries. We generated a rodent model of CPS by making unilateral electrolytic or demyelinating lesions centered on the spinothalamic tract in rats. Thermal hyperalgesia and mechanical allodynia occurred in both hind paws and forepaws by 7 d postlesion and were maintained >31 d. Field potentials in the ventral posterior lateral nucleus (VPL) in thalamic brain slices from lesioned animals displayed an increased probability of burst responses. Ethosuximide, a T-type calcium channel blocker, eliminated busting in lesioned thalamic slices and attenuated lesion-induced hyperalgesia and allodynia. We conclude that CPS in this model results from an increase in the excitability of thalamic nuclei that have lost normal ascending inputs as the result of a spinal cord injury and suggest that ethosuximide will relieve human CPS by restoring normal thalamic excitability.
