Experimental neurology
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Experimental neurology · Oct 2006
Pain with no gain: allodynia following neural stem cell transplantation in spinal cord injury.
Transplantation of neural stem cells (NSCs) in the injured spinal cord has been shown to improve functional outcome; however, recent evidence has demonstrated forelimb allodynia following transplantation of embryonic NSCs. The aim of this study was to investigate whether transplantation of murine C17.2 NSCs alone or transfected with glial-derived neurotrophic factor (C17.2/GDNF) would induce allodynia in transplanted spinal cord-injured animals. One week after a T8-level spinal cord injury (SCI), C17.2, C17.2/GDNF or normal saline was injected at the injury site. ⋯ Sprouting of nocioceptive afferents occurred rostral to the injury/transplantation site only in allodynic animals, suggesting a principal role in this aberrant pain state. Further, a difference in the degree of allodynia was noted between C17.2- and C17.2/GDNF transplant-treated groups; this difference correlated with the level of CGRP/GAP43 immunoreactivity and sprouting observed in the cervicothoracic dorsal horns. Both allodynia- and CGRP/GAP43-positive afferent sprouting were less in the C17.2/GDNF group compared to the C17.2 group, suggesting a possible protective or analgesic effect of GDNF on post-injury neuropathic pain.
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Experimental neurology · Oct 2006
Paclitaxel- and vincristine-evoked painful peripheral neuropathies: loss of epidermal innervation and activation of Langerhans cells.
Experimental painful peripheral neuropathies produced by the chemotherapeutic drugs, paclitaxel and vincristine, are produced by relatively low doses that do not cause axonal degeneration in peripheral nerve. Using quantitative immunolabeling with the PGP9.5 antibody, we have investigated whether these painful neuropathies might be associated with degeneration that is confined to the region of the sensory fiber's receptor terminals in the skin. Because complete and partial nerve transections are known to cause an increase in PGP9.5 in epidermal Langerhans cells (LCs), we also examined whether this effect occurs in chemotherapy-treated animals. ⋯ However, neither loss of IENF nor an increase in PGP9.5-positive LCs was found in rats with a painful peripheral neuropathy evoked by the anti-HIV agent, 2',3'-dideoxycytidine. We also confirmed that there is a decrease in IENF and an increase in PGP9.5-positive LCs in rats with neuropathic pain following a partial nerve injury (CCI model) and in rats with a complete sciatic nerve transection. Partial degeneration of the intraepidermal innervation suggests mechanisms that might produce chemotherapy-evoked neuropathic pain, and activation of cutaneous LCs suggests possible neuroimmune interactions that might also have a role.
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Experimental neurology · Oct 2006
Contralesional neural plasticity and functional changes in the less-affected forelimb after large and small cortical infarcts in rats.
Some studies have found that unilateral cerebral damage produces significant deficits in the ipsilesional, "less-affected", body side. Other studies have found that such damage results in a paradoxical hyperfunctionality of the ipsilesional body side and a facilitation of learning-induced neuroplastic changes in the contralesional motor cortex. The purpose of this study was to determine whether these effects co-exist and/or vary with lesion severity. ⋯ These effects were correlated with reaching performance. Therefore, enhanced motor skill learning in the "less-affected" forelimb and contralesional neuroplastic changes are muted after larger lesions and co-exist with ipsilesional impairments. These effects may be related to a denervation-induced neural restructuring of the contralesional cortex that both disrupts pre-existing motor engrams and facilitates the establishment of new ones.
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Experimental neurology · Sep 2006
Relationship of calpain-mediated proteolysis to the expression of axonal and synaptic plasticity markers following traumatic brain injury in mice.
The role of neuronal plasticity and repair on the final functional outcome following traumatic brain injury (TBI) remains poorly understood. Moreover, the relationship of the magnitude of post-traumatic secondary injury and neurodegeneration to the potential for neuronal repair has not been explored. To address these questions, we employed Western immunoblotting techniques to examine how injury severity affects the spatial and temporal expression of markers of axonal growth (growth-associated protein GAP-43) and synaptogenesis (pre-synaptic vesicular protein synaptophysin) following either moderate (0.5 mm, 3.5 M/s) or severe (1.0 mm, 3.5 M/s) lateral controlled cortical impact traumatic brain injury (CCI-TBI) in young adult male CF-1 mice. ⋯ Supporting this hypothesis is the fact that GAP-43 is a substrate for calpain along with our data demonstrating that calpain-mediated degradation of the cytoskeletal protein, alpha-spectrin, is approximately 10 times greater in ipsilateral hippocampal tissue following severe compared to moderate CCI-TBI. Thus, TBI severity has a differential effect on the injury-induced neurorestorative response with calpain activation being one putative factor contributing to neuroregenerative failure following severe CCI-TBI. If true, then calpain inhibition may lead to both neuroprotective effects and an enhancement of neuronal plasticity/repair mechanisms post-TBI.
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Experimental neurology · Sep 2006
Loss of the astrocyte glutamate transporter GLT1 modifies disease in SOD1(G93A) mice.
Recent studies have highlighted the role of astrocytes in the development of motor neuron disease in animal models. The astrocyte glutamate transporter GLT1 is responsible for a significant portion of glutamate transport from the synaptic cleft; regulating synaptic transmission and preventing glutamate excitotoxicity. While previous studies have demonstrated reductions in GLT1 with SOD1-mediated disease progression, it is not well established whether a reduction in this astrocyte-specific transporter alters the pathobiology of motor neuron degeneration in the SOD1(G93A) mouse. ⋯ Dramatic losses of the GLT1 protein and reduced glutamate transport in the lumbar spinal cords of the SOD1(G93A)/GLT1+/- animals were also observed. GLT1 was not significantly changed in cortices from these animals suggesting that the effect of mutant SOD1 on GLT1 production/function was largely targeted to spinal cord rather than cortical astrocytes. This study suggests that astrocytes, and the astrocyte glutamate transporter GLT1, play a role in modifying disease progression and motor neuron loss in this model.