Articles: neuropathic-pain.
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Anesthesia and analgesia · Apr 2014
Differential suppression of intracranial self-stimulation, food-maintained operant responding, and open field activity by paw incision and spinal nerve ligation in rats.
Detection of ongoing spontaneous pain behaviors in laboratory animals remains a research challenge. Most preclinical pain studies measure elicited behavioral responses to an external noxious stimulus; however, ongoing spontaneous pain in humans and animals may be unrelated to hypersensitivity, and likely diminishes many behaviors, particularly motivated behaviors, that we hypothesize will decrease after induction of acute and chronic pain. ⋯ The acute effects of INC on decreasing lever pressing for VTA ICSS and FR (1-2 days after incision) correspond to the timeframe in which ongoing spontaneous pain is expected to occur after INC. Therefore, these decreases are likely mediated by ongoing spontaneous pain, which may be unrelated to mechanical hypersensitivity that persists for up to 4 days after INC. PWT is decreased similarly by SNL, yet operant behavior (lever pressing for VTA ICSS and FR) was not decreased by SNL. SNL, but not INC, decreased rearing behavior but not total distance traveled during OFA. This further indicates that the presence and the extent of hypersensitivity are not predictive of many behavioral changes in rats thought to be mediated by the presence of ongoing pain. Surprisingly, the behavioral effects of INC are not exacerbated in SNL rats. These data support the growing belief that acute pain models produce short-lived spontaneous pain behaviors that are often less pronounced or absent in neuropathic pain models, and highlight the need for assessment of both evoked and nonevoked pain behaviors in developing future therapies for acute and chronic pain.
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Semin. Arthritis Rheum. · Apr 2014
History of knee surgery is associated with higher prevalence of neuropathic pain-like symptoms in patients with severe osteoarthritis of the knee.
Neuropathic pain (NP) mechanisms contribute to the pain experience in osteoarthritis (OA). We aimed to characterise the factors that contribute to NP-like symptoms in knee OA patients. ⋯ NP-like symptoms are highly prevalent in patients with clinically severe painful OA and are a significant contributor to decreased quality of life and higher pain intensity. The cross-sectional association with previous history of knee surgery suggests that some of the NP-like symptoms may result from nerve damage.
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Previous data showed that neuropathic pain induced by mechanical lesion of peripheral nerves responds differently to alleviating drugs at cephalic versus extracephalic level. Because neuropathic pain evoked by anti-cancer drugs differs from that triggered by mechanical nerve lesion, we investigated whether differences between cephalic and extracephalic levels could also be characterized in rodents rendered neuropathic by treatment with the anti-cancer platinum derivative oxaliplatin. C57BL/6J mice received two injections and Sprague-Dawley rats three injections of oxaliplatin (10 mg/kg, i.p.) or its vehicle, with three days intervals. ⋯ Among the various markers investigated, only TRPA1 transcript was upregulated in ganglia of oxaliplatin-treated rats. These data showed that oxaliplatin induced supersensitivity to various stimuli in both cephalic and extra-cephalic territories in rodents. Regional differences in the efficacy of drugs to alleviate oxaliplatin-induced allodynia/hyperalgesia further support the idea that mechanisms underlying neuropathic pain have peculiarities at cephalic versus extra-cephalic level.
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Intrathecal drug delivery (IDD) system with implantable pumps has been used to treat cancer-related pain as well as noncancer-related chronic pain. Opioids, including morphine and hydromorphone, are the most commonly used intrathecal (IT) agents. Although technology, techniques, and knowledge of IDD have improved, dose escalation occurs relatively rapidly in noncancer pain. ⋯ Annual increases in daily opioid dosage were higher among patients with neuropathic pain than among patients with other modalities; we also found no evidence of difference in annual pain reduction.
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Background and purpose Conventional neurophysiological techniques do not assess the function of nociceptive pathways and are inadequate to detect abnormalities in patients with small-fiber damage. This overview aims to give an update on the methods and techniques used to assess small fiber (Aδ- and C-fibers) function using evoked potentials in research and clinical settings. Methods Noxious radiant or contact heat allows the recording of heat-evoked brain potentials commonly referred to as laser evoked potentials (LEPs) and contact heat-evoked potentials (CHEPs). ⋯ Recent studies suggest that both CHEPs and pinprick-evoked potentials may also be convenient tools to assess sensitization of the nociceptive system. Conclusions In future studies, small-fiber evoked potentials may also be used in studies that aim to understand pain mechanisms including different neuropathic pain phenotypes, such as cold- or touch-evoked allodynia, and to identify predictors of response to pharmacological pain treatment. Implications Future studies are needed for some of the newly developed methods.