Articles: neuropathic-pain.
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Preclinical assessment of pain has increasingly explored operant methods that may allow behavioral assessment of ongoing pain. In animals with incisional injury, peripheral nerve block produces conditioned place preference (CPP) and activates the mesolimbic dopaminergic reward pathway. We hypothesized that activation of this circuit could serve as a neurochemical output measure of relief of ongoing pain. ⋯ In contrast, ketorolac or naproxen produced increased NAc DA in animals with incisional but not neuropathic pain. Increased extracellular NAc DA release was consistent with CPP and was observed selectively with treatments commonly used clinically for post-surgical or neuropathic pain. Evaluation of NAc DA efflux in animal pain models may represent an objective neurochemical assay that may serve as a biomarker of efficacy for novel pain-relieving mechanisms.
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Neuropathic pain after peripheral nerve injury is characterized by loss of inhibition in both peripheral and central pain pathways. In the adult nervous system, the Na(+)-K(+)-2Cl(-) (NKCC1) and neuron-specific K(+)-Cl(-) (KCC2) cotransporters are involved in setting the strength and polarity of GABAergic/glycinergic transmission. After nerve injury, the balance between these cotransporters changes, leading to a decrease in the inhibitory tone. ⋯ We also found an increase in NKCC1 expression in the DRG and a downregulation of KCC2 in spinal cord after injury, accompanied by later decrease of KCC2 levels in higher projection areas (VPL and S1) from 2 weeks postinjury, correlating with neuropathic pain signs. Administration of bumetanide (30 mg/kg) during 2 weeks following sciatic nerve lesion prevented the previously observed changes in the spinothalamic tract projecting areas and the appearance of hyperalgesia. In conclusion, the present results indicate that changes in NKCC1 and KCC2 in DRG, spinal cord, and central pain areas may contribute to development of neuropathic pain.
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Phys Med Rehabil Clin N Am · Aug 2014
ReviewChronic neuropathic pain in SCI: evaluation and treatment.
Chronic neuropathic pain develops in approximately 40% of people after a spinal cord injury (SCI) and is notoriously difficult to treat. Because of the frequent presence of more than one pain type and the complex mechanisms and symptoms associated with pain in individuals with SCI, a thorough evaluation is important. This review includes an overview of the most recent guidelines for evaluating and classifying pain, suggestions for standardizing outcome measures for clinical use, and a review of the positive and negative evidence for pharmacologic and nonpharmacologic interventions to consider when treating individuals with SCI and chronic neuropathic pain.
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5% lidocaine medicated plasters are a topical option in the treatment of peripheral neuropathic pain, as monotherapy or as an adjunct to systemic medication. This study sought to determine the impact of lidocaine plaster use on self-reported pain, functioning and patient satisfaction within a large teaching hospital. ⋯ The results of this study need to be considered within the context of a self-reported survey. However, pain, functioning and patient satisfaction were significantly improved in current users of 5% lidocaine medicated plasters.