Neuroreport
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Comparative Study
Heat hyperalgesia following partial sciatic ligation in rats: interacting nature and nurture.
As in humans, levels of neuropathic pain produced by nerve injury are highly variable among animals. This variability was attributed to genetic and environmental factors. ⋯ We show that heat sensitivity of intact rats and levels of heat hyperalgesia of PSL-injured rats were highly variable across eight different rat strains and seven different diets. Thus, genetic and environmental variables interact in determination of levels of chronic neuropathic sensory disorders in rats.
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Clinical Trial Controlled Clinical Trial
Degeneration of nociceptive nerve terminals in human peripheral neuropathy.
Patients with peripheral neuropathy have symptoms involving small-diameter nociceptive nerves and elevated thermal thresholds. Nociceptive nerves terminate in the epidermis of the skin and are readily demonstrated with the neuronal marker, protein gene product 9.5 (PGP 9.5). To investigate the pathological characteristics of elevated thermal thresholds, we performed PGP 9.5 immunocytochemistry on 3 mm punch skin biopsies (the forearm and the leg) from 55 normal subjects and 35 neuropathic patients. ⋯ The proportion of neuropathic patients with reduced epidermal nerve densities was larger than the proportion of neuropathic patients with elevated thermal thresholds. These results indicated that degeneration of epidermal nerve terminals preceded the elevation of thermal thresholds. Skin biopsy together with immunocytochemical demonstration of epidermal innervation offers a new approach to evaluate small-fiber sensory neuropathy.
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We tested the hypothesis that the decrease in spinal levels of SP and CGRP after peripheral nerve injury is related to neuropathic pain. We compared two groups of rats, both of which were subjected to unilateral transection of the inferior and superior caudal trunks between the S1 and S2 spinal nerves. ⋯ The decrease in immunoreactivity of CGRP and SP in the S1 dorsal horn (injured segment) was not significantly different between the two groups. These results suggest that the decrease in spinal levels of CGRP and SP after peripheral nerve injury is not related to neuropathic pain.
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Humans can perform purposeful hand actions even blindly in the dark, perhaps using mental images of the hand. To demonstrate such subjective body images, this study describes the activities of bimodal (somatosensory and visual) neurons in the monkey intraparietal cortex. ⋯ Furthermore, when the hand was moved invisibly under the plate, the v-RF moved over the plate to follow the invisible s-RF. Thus, monkeys can maintain and update subjective body images in the mind, and they are coded by intraparietal bimodal neurons.
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Clinically effective drug treatments for spinal cord injury (SCI) remain unavailable. Agmatine, an NMDA receptor antagonist and inhibitor of nitric oxide synthase (NOS), is an endogenous neuromodulator found in the brain and spinal cord. ⋯ The results suggest the importance of future therapeutic strategies encompassing the use of single drugs with multiple targets for the treatment of acute SCI. The therapeutic targets of agmatine (NMDA receptor and NOS) have been shown to be critically linked to the pathophysiological sequelae of CNS injury and this, combined with the non-toxic profile, lends support to agmatine being considered as a potential candidate for future clinical applications.