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Effects of repeated dosing with mechanistically distinct antinociceptive ligands in a rat model of neuropathic spinal cord injury pain.

ABSTRACT: A lack of efficacy of some analgesic drugs has been previously described in rats with neuropathic spinal cord injury (SCI) pain. It has been suggested that repeated dosing in these animals over time may eventually lead to efficacy. However, it is also possible that efficacy may diminish over time with repeated dosing. This study evaluated the efficacy of various drugs upon repeated dosing over time in a rat model of SCI pain. Four weeks following an acute spinal cord compression at the mid-thoracic level, rats developed decreased hind paw withdrawal threshold, suggestive of below level neuropathic hypersensitivity. Either cannabinoid (CB) receptor agonist CP 55,940, the anticonvulsant carbamazepine or gabapentin, the antidepressant amitriptyline or vehicle was administered over a period of 7 days. Neither carbamazepine nor amitriptyline demonstrated efficacy either after a single or repeated dosing. Beginning with a 50% efficacious dose of gabapentin, the effect of gabapentin in SCI rats neither increased nor decreased over the treatment period. The antinociceptive effect of CP 55,940 was maintained for the entire treatment period, which was mediated by CB1 but not CB2 receptors. The current data suggest that sustained antinociception can be obtained with some drugs in rats with neuropathic SCI pain. Furthermore, the current data do not substantiate the notion that repeated treatment with initially ineffective drugs will eventually lead to efficacy; treatments that are not acutely effective are unlikely to demonstrate clinical efficacy.

SUBMITTER: Hama AT

PROVIDER: S-EPMC4184706 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature

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Effects of repeated dosing with mechanistically distinct antinociceptive ligands in a rat model of neuropathic spinal cord injury pain.

Hama Aldric T AT Pearson James P JP Sagen Jacqueline J

Pharmacology research & perspectives 20140313 2

A lack of efficacy of some analgesic drugs has been previously described in rats with neuropathic spinal cord injury (SCI) pain. It has been suggested that repeated dosing in these animals over time may eventually lead to efficacy. However, it is also possible that efficacy may diminish over time with repeated dosing. This study evaluated the efficacy of various drugs upon repeated dosing over time in a rat model of SCI pain. Four weeks following an acute spinal cord compression at the mid-thora ...[more]

PMID: 25505583

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Project description:Objective: Chronic pain is a major problem in patients with spinal cord injury (SCI). According to different studies, approximately 70% of patients with SCI experience persistent pain. Although previous gene expression profiling studies have been conducted in animal models, gene expression profiling study in human whole blood has not been reported yet. The objective of this study was to define the gene expression profile of neuropathic pain in spinal cord injured patients. Materials and Methods: We performed gene expression analysis including 20.000 genes using Affymetrix GeneChip® Primeview™ Human Gene Expression Arrays. For confirmation of expression levels of selected genes, we performed real time polymerase chain reaction. We gathered samples from periferic blood mononuclear cells. Data of twelve patients with intractable neuropathic pain was compared with thirteen patients who don’t have pain. All patients have complete injuries with a level of injury above T5. Results: A total of 16 differentially expressed genes including 9 up-regulated and 7 down-regulated were obtained with a cut-off degree at 4 fold change. EIF1AY, RPS4Y1, DDX3Y, RPL31, ETS1, KLF3, JUN, CYorf15B, and ERAP2 were in up-regulated and HLA-C, XIST, C4BPA, FAM118A, ZNF506, OVOS2, and C1D were in down-regulated group. KEGG pathway database showed that 14.6% of genes were enriched in the nodes of immune system. Real time polymerase chain reaction analyses did not increase to statistically significant levels for confirmation of gene expression analyze results. Conclusions: Considering these data, findings of this first gene expression study in humans with SCI might provide valuable information for future targets for understanding neuropathic pain pathogenesis. The results of gene expression analyses were not confirmed by real time polymerase chain reaction. Studies with larger sample size are needed for confirmation. This is a cross-sectional study with a control group. Patients were divided into two groups according to intractable neuropathic pain existence.There were 12 patients in group A (Patients with pain) and 13 patients in control group.

Dataset Information

Effects of repeated dosing with mechanistically distinct antinociceptive ligands in a rat model of neuropathic spinal cord injury pain.

Publications

Effects of repeated dosing with mechanistically distinct antinociceptive ligands in a rat model of neuropathic spinal cord injury pain.

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